@article{Ogoshi2024,

title = {Learning from machine learning: the case of band-gap directness in semiconductors},

author = {Elton Ogoshi and Mário Popolin-Neto and Carlos Mera Acosta and Gabriel M. Nascimento and João N. B. Rodrigues and Osvaldo N. Oliveira and Fernando V. Paulovich and Gustavo M. Dalpian},

url = {https://link.springer.com/article/10.1007/s43939-024-00073-x},

doi = {10.1007/s43939-024-00073-x},

issn = {2730-7727},

year  = {2024},

date = {2024-12-00},

urldate = {2024-12-00},

journal = {Discov Mater},

volume = {4},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {Having a direct or indirect band gap can influence the potential applications of a semiconductor, for indirect band gap materials are usually not suitable for optoelectronic devices. Even though this is a fundamental property of semiconducting materials, discussed in textbooks, no unified theory exists to explain why a material has a direct or indirect band gap. Here we used an interpretable machine learning model, the multiVariate dAta eXplanation (VAX) method, to gather information from a dataset of materials extracted from the Materials Project. The dataset contains more than 10000 entries, and atomic properties such as the number of electrons, electronic affinity and orbital energies were used as features to build random forest models that successfully explain the directness of the band gaps. Our results indicate that symmetry is an important feature that dictates the target property, which is the reason why our analysis is made based on sub-groups with similar structures. These sub-groups include materials with zincblende, rocksalt, wurtzite, and perovskite structures. Besides the symmetry of the materials, the existence or not of d bands and the relative energy of atomic orbitals were found to be important in defining whether a material’s band gap is direct or indirect. In conclusion, interpretable machine learning methods such as VAX can be useful in obtaining physical interpretation from materials databases.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Farigliano2024,

title = {Phase transitions in CsPbBr3: evaluating perovskite behavior over different time scales},

author = {Lucas Martin Farigliano and Fabio Negreiros Ribeiro and Gustavo M. Dalpian},

url = {https://pubs.rsc.org/en/content/articlehtml/2024/ma/d4ma00216d},

doi = {10.1039/d4ma00216d},

issn = {2633-5409},

year  = {2024},

date = {2024-07-15},

urldate = {2024-07-15},

journal = {Mater. Adv.},

volume = {5},

number = {14},

pages = {5794--5801},

publisher = {Royal Society of Chemistry (RSC)},

abstract = {Halide perovskites have gained relevance in the field of solar cells due to their remarkable electro-optical properties, which enable efficient conversion of solar energy into electricity. Despite their promising characteristics, challenges such as long-term stability and structural complexity demand exceptional attention and dedication in the research on these materials. Their inherent soft nature, high atom mobility (especially of the halides) and the unconventional dynamics of structural motifs (halide octahedra) make them interesting from a fundamental point of view as well. The study focuses on understanding phase transitions in CsPbBr3 perovskite, considering the importance of the dynamic properties it exhibits. The phase transitions of the CsPbBr3 perovskite were studied through ab initio NPT molecular dynamics simulations considering several different temperatures. By taking into account the average structures over a simulation time of 45 ps after thermalization, we predict phase transitions between 300 and 325 K, as well as between 400 and 450 K, in line with previous experimental findings reported in the literature. Furthermore, through the analysis of the angles within the octahedron (Br–Pb–Br) and between octahedra (Pb–Br–Pb), the mechanism underlying the phase transitions is understood, and the structural anomalies previously reported [Svirskas et al., J. Mater. Chem. A, 2020, 8, 14015–14022] near 220 K are identified. In addition to the results obtained by performing long-time averages, we also conducted an analysis of the implications of using different time windows when calculating the average properties of interest. In this case, we observed a more complex pattern, where the material exhibits various structures depending on the exposure time and temperature, which aligns with the polymorphic nature of these materials. Our results show that, depending on the type of experiment that is being performed, different analysis, with averages considered over different times, must be performed. Long-time averages can be compared to X-ray diffraction experiments, while short-time averages should be compared to experiments that track the local structure of the material, such as PDF or Raman. Our results also indicate that phase transitions in CsPbBr3 are not as abrupt as previously considered, posing new challenges for the experimental observation of these features.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sabino2024,

title = {Impact of symmetry breaking and spin-orbit coupling on the band gap of halide perovskites},

author = {Fernando P. Sabino and Xin Gang Zhao and Gustavo M. Dalpian and Alex Zunger},

url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.110.035160},

doi = {10.1103/physrevb.110.035160},

issn = {2469-9969},

year  = {2024},

date = {2024-07-00},

urldate = {2024-07-00},

journal = {Phys. Rev. B},

volume = {110},

number = {3},

publisher = {American Physical Society (APS)},

abstract = {Halide perovskite (HP) materials have recently emerged as a class of semiconductors with immense promise for various optoelectronic applications, ranging from solar cells to light-emitting diodes. One of the unique attributes of HPs is their tunable band gaps with different factors governing their value. The first factor is related to relativistic corrections [“mass-Darwin,” connected to the 𝑛⁢𝑠2 lone pairs, and spin-orbit coupling (SOC)] that induce an orbital shift or degeneracy splitting, resulting in a band-gap reduction. The second factor involves the structural configuration: in HPs the local symmetry of each Wyckoff position tends to be broken, inducing an opening of the band gap. Based on high-throughput density functional theory calculations, this paper systematically studies a possible self-cancelation on the band-gap correction for HPs when the polymorphous configuration—structural effects—and the SOC—electronic effects—are included. Our results indicate that the nature of interplay between SOC and symmetry breaking (SB) is that they are independent decoupling effects to describe the band-gap magnitude in halide perovskites. As a result of that, we observe a transitivity of the band-gap description; i.e., if we know the band gap of halide perovskites without SB and SOC, we can independently add the effects of band-gap reduction due to SOC and band-gap opening due to SB, regardless of the order in which these effects are considered.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bandeira2024,

title = {CO2 Reduction beyond Copper-Based Catalysts: A Natural Language Processing Review from the Scientific Literature},

author = {Lucas Bandeira and Henrique Ferreira and James Moraes de Almeida and Amauri Jardim de Paula and Gustavo M. Dalpian},

url = {https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.3c06920},

doi = {10.1021/acssuschemeng.3c06920},

issn = {2168-0485},

year  = {2024},

date = {2024-03-18},

urldate = {2024-03-18},

journal = {ACS Sustainable Chem. Eng.},

volume = {12},

number = {11},

pages = {4411--4422},

publisher = {American Chemical Society (ACS)},

abstract = {Carbon dioxide (CO2) is a prominent greenhouse gas that contributes significantly to global warming. To combat this issue, one strategy is the conversion of CO2 into alcohols and hydrocarbons, which can be used as fuels and chemical feedstocks. Consequently, a substantial volume of scientific literature has been dedicated to investigating different materials and reaction conditions to facilitate the CO2 reduction reaction (CO2RR) into these so-called high-value products. However, the vastness of this literature makes it challenging to stay updated on recent discoveries and review the most promising materials and conditions that have been explored. To address this issue, we applied natural language processing tools to extract valuable data from 7292 published articles in the scientific literature. Our analysis revealed the emergence of new materials such as cesium–lead–bromide perovskites and bismuth oxyhalides that have been recently used in the CO2RR and identified Bi-based catalysts as the most selective for HCOO– production. Furthermore, we gleaned insights into the composition of other elements and materials commonly employed in the CO2RR, their relationship to product distribution, and the prevalent electrolytes used in the CO2 electrochemical reduction. Our findings can serve as a foundation for future investigations in the realm of catalysts for CO2RRs, offering insights into the most promising materials and conditions to pursue further research.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Morais2024d,

title = {Rashba Spin Splitting Limiting the Application of 2D Halide Perovskites for UV-Emitting Devices},

author = {Eliane A. Morais and Naidel A. M. S. Caturello and Maykon A. Lemes and Henrique Ferreira and Fabio F. Ferreira and Jose J. S. Acuña and Sergio Brochsztain and Gustavo M. Dalpian and Jose A. Souza},

url = {https://pubs.acs.org/doi/abs/10.1021/acsami.3c16541},

doi = {10.1021/acsami.3c16541},

issn = {1944-8252},

year  = {2024},

date = {2024-01-24},

urldate = {2024-01-24},

journal = {ACS Appl. Mater. Interfaces},

volume = {16},

number = {3},

pages = {4261--4270},

publisher = {American Chemical Society (ACS)},

abstract = {Layered lead halide perovskites have attracted much attention as promising materials for a new generation of optoelectronic devices. To make progress in applications, a full understanding of the basic properties is essential. Here, we study 2D-layered (BA)2PbX4 by using different halide anions (X = I, Br, and Cl) along with quantum confinement. The obtained cell parameter evolution, supported by experimental measurements and theoretical calculations, indicates strong lattice distortions of the metal halide octahedra, breaking the local inversion symmetry in (BA)2PbCl4, which strongly correlates with a pronounced Rashba spin-splitting effect. Optical measurements reveal strong photoluminescence quenching and a drastic reduction in the PL quantum yield in this larger band gap compound. We suggest that these optical results are closely related to the appearance of the Rashba effect due to the existence of a local electric dipole. The results obtained in ab initio calculations showed that the (BA)2PbCl4 possesses electrical polarization of 0.13 μC/cm2 and spin-splitting energy of about 40 meV. Our work establishes that local octahedra distortions induce Rashba spin splitting, which explains why obtaining UV-emitting materials with high PLQY is a big challenge.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bezzon2023b,

title = {Crystal structure determination and DFT analysis of doxorubicin hydrochloride for controlled-release drug formulations},

author = {Vinícius Danilo Nonato Bezzon and Naidel Antonio Moreira dos Santos Caturello and Gustavo M. Dalpian and Fabio Furlan Ferreira},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0022286023015028},

doi = {10.1016/j.molstruc.2023.136412},

issn = {0022-2860},

year  = {2023},

date = {2023-12-00},

urldate = {2023-12-00},

journal = {Journal of Molecular Structure},

volume = {1294},

publisher = {Elsevier BV},

abstract = {Doxorubicin hydrochloride (DOX) is a widely used chemotherapeutic drug that inhibits the growth of cancer cells. Many DOX-based controlled-release systems have been proposed to reduce toxicity. However, knowledge of its crystal structure is essential for optimizing drug release processes and designing co-crystals or salts with different release properties. Although DOX has been extensively studied, no crystal structure is available in the Cambridge Structural Database or literature. In this work, we determine the crystal structure of DOX using a simulated annealing approach based on powder X-ray diffraction data. We confirm its validation by Rietveld refinement and molecular cohesion by using a molecular geometry check tool. We also use density functional theory to optimize the DOX structure and obtain the minimum energy conformation, H-bond donor/acceptor species, charge localization, and crystal structure parameters. This study provides essential structural information on DOX that can be used to rationalize new modified-release dosage forms and to design co-crystals or salts with different release properties.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Espinosa-García2023,

title = {Intrinsic defects in sulvanite compounds: The case of transparent Cu3TaS4 and absorbing Cu3VSe4},

author = {W.F. Espinosa-García and Gustavo M. Dalpian and J.M. Osorio-Guillén},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0925838823035673},

doi = {10.1016/j.jallcom.2023.172264},

issn = {0925-8388},

year  = {2023},

date = {2023-12-00},

urldate = {2023-12-00},

journal = {Journal of Alloys and Compounds},

volume = {969},

publisher = {Elsevier BV},

abstract = {Sulvanites are semiconducting compounds with the chemical formula Cu3TMX4 where TM = V, Nb, Ta; X = S, Se, Te. Semiconductor electronic and optical properties are highly influenced by intrinsic defects such as vacancies, antisites, and atoms residing in interstitial positions inside the crystal structure. Even though intrinsic defects are extremely important, very little is known about defects in sulvanites. Here we report the properties of all intrinsic defects in two representative sulvanite compounds (Cu3TaS4 and Cu3VSe4) by using computational quantum mechanical methods. Our results indicate that Cu vacancies are the most frequent defects in these compounds, also responsible for limiting the possibility of their n-type doping and setting the pinning of the Fermi energy to positions close to the valence band. These results explain why as-grown sulvanites are usually p-type and open a path to search for ways to design and tune the properties of these compounds.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sabino2023,

title = {Light‐Induced Frenkel Defect Pair Formation Can Lead to Phase‐Segregation of Otherwise Miscible Halide Perovskite Alloys},

author = {Fernando P. Sabino and Gustavo M. Dalpian and Alex Zunger},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202301539},

doi = {10.1002/aenm.202301539},

issn = {1614-6840},

year  = {2023},

date = {2023-11-00},

urldate = {2023-11-00},

journal = {Advanced Energy Materials},

volume = {13},

number = {44},

publisher = {Wiley},

abstract = {Alloys of ABX3 halide perovskites (HP) exhibit unique phase behavior compared to traditional III-V and II-VI semiconductor alloys used in solar cells. While the latter typically have good mutual miscibility when their mixed components are size matched, and phase-segregate when size mismatched, HP alloys show good miscibility in the dark but can phase-segregate under light. Quantum mechanical calculations described herein reveal light-induced defect formation and migration hold the key. Specifically, the interaction between a halogen vacancy VX with halogen interstitial Xi forming together a Frenkel-pair defect emerges as the enabler for phase-segregation in HP alloys. At a threshold bromine composition in the Br-I alloys, the photogenerated holes in the valence band localize, creating thereby a doubly-charged iodine Frenkel-pair (VI + Ii)2+. Faster migration of iodine over bromine interstitial into the vacant iodine VI site leads to the formation of iodine-rich and iodine-depleted regions, establishing phase-segregation. Removal of the mobile defects–the agent of segregation–by dark thermal annealing, supplies the opposing force, leading to reversal of phase-segregation. This atomistic understanding can enable some control of the phase-segregation by selecting substituting elements on the B site–such as replacing some Pb by Sn–that are unable to form stable Frenkel defects.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yadav2023,

title = {First-principles investigations of 2D materials: Challenges and best practices},

author = {Asha Yadav and Carlos Mera Acosta and Gustavo M. Dalpian and Oleksandr I. Malyi},

url = {https://www.cell.com/matter/abstract/S2590-2385(23)00237-0},

doi = {10.1016/j.matt.2023.05.019},

issn = {2590-2385},

year  = {2023},

date = {2023-09-00},

urldate = {2023-09-00},

journal = {Matter},

volume = {6},

number = {9},

pages = {2711--2734},

publisher = {Elsevier BV},

abstract = {2D materials have garnered significant interest due to their unique properties and potential applications in electronics, energy storage, and nanotechnology. However, experimental synthesis is still based on the trial-and-error Edisonian approach, and first-principles calculations have become essential for understanding potential material realization, predicting their properties, and even designing new nanomaterials for device applications. This review provides a comprehensive overview of recent progress in electronic structure theory investigations of 2D materials, addresses challenges in accurate calculations of materials properties and materials stability and suggesting best practices for future work. This is all done to reduce the gap between theoretical predictions and experimental realizations to unlock the full potential of 2D materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bonadio2023b,

title = {Comparing the Cubic and Tetragonal Phases of MAPbI3 at Room Temperature},

author = {Ariany Bonadio and Fernando P. Sabino and André L. M. Freitas and Marissol R. Felez and Gustavo M. Dalpian and Jose A. Souza},

url = {https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.3c00874},

doi = {10.1021/acs.inorgchem.3c00874},

issn = {1520-510X},

year  = {2023},

date = {2023-05-15},

urldate = {2023-05-15},

journal = {Inorg. Chem.},

volume = {62},

number = {19},

pages = {7533--7544},

publisher = {American Chemical Society (ACS)},

abstract = {Stability and maintenance of the crystal structure are the main drawbacks of the application of organic–inorganic perovskites in photovoltaic devices. The ΔT = 62 K robust shift of the structural phase transition observed here allows us to conduct a comprehensive study at room temperature of the tetragonal versus cubic phase on MAPbI3. The absence of the shift in the cubic transition for all-inorganic CsPbI3 samples confirms the importance of both orientation and dynamics of the organic cations. Our results provide a unique opportunity to evaluate the physical properties of both cubic and tetragonal phases of MAPbI3 at the same temperature, eliminating different phonon effects as possible causes for different properties. Besides higher electrical resistivity, the perovskite cubic phase presents a faster charge carrier lifetime than the tetragonal phase and partial PL quenching, pointing toward increased trap-assisted nonradiative recombination. The light absorption coefficient in the cubic phase is larger than the absorption in the tetragonal phase in the green region.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{MartinsFreitas2023b,

title = {Finite-Size Effects on Cs3Cu2I5 0D Electronic Nanostructures for Ultraviolet-Emitting Applications},

author = {Andre Luiz Martins Freitas and Aryane Tofanello and Fernando Pereira Sabino and Marissol Rodrigues Felez and Eliane Aparecida Morais and Sergio Brochsztain and Jose Javier Sáez Acuña and Gustavo M. Dalpian and Jose Antonio Souza},

url = {https://pubs.acs.org/doi/abs/10.1021/acsanm.3c00242},

doi = {10.1021/acsanm.3c00242},

issn = {2574-0970},

year  = {2023},

date = {2023-05-12},

urldate = {2023-05-12},

journal = {ACS Appl. Nano Mater.},

volume = {6},

number = {9},

pages = {7196--7205},

publisher = {American Chemical Society (ACS)},

abstract = {The potential to produce ultraviolet (UV) light-emitting devices has attracted significant interest in interdisciplinary fields, particularly in the use of 0D halide nanostructures due to their straightforward synthesis methods and exceptional efficiency in optoelectronics. Here, we present a systematic study involving nanostructure synthesis and significant changes in the electronic structure caused by finite-size effects. We have focused on the investigation of size effects on the UV-light emitting properties of all-inorganic Cs3Cu2I5 halide. We observe that bulk particles present a pronounced bright-blue emission at 440 nm with a high quantum yield of 80%. Very small quantum dots nanostructures (6–10 nm) reveal a significant shift of the photoluminescence peak down to ∼395 nm, close to the UV-A region, but with a quantum yield reduction of 10%. Surface engineering to obtain very small nanoparticles free from defects at the nanocrystal surface is crucial for maintaining a high quantum efficiency, allowing their use in UV-emitting devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nascimento2022e,

title = {High-throughput inverse design and Bayesian optimization of functionalities: spin splitting in two-dimensional compounds},

author = {Gabriel M. Nascimento and Elton Ogoshi and Adalberto Fazzio and Carlos Mera Acosta and Gustavo M. Dalpian},

url = {https://www.nature.com/articles/s41597-022-01292-8},

doi = {10.1038/s41597-022-01292-8},

issn = {2052-4463},

year  = {2022},

date = {2022-12-00},

urldate = {2022-12-00},

journal = {Sci Data},

volume = {9},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {The development of spintronic devices demands the existence of materials with some kind of spin splitting (SS). In this Data Descriptor, we build a database of ab initio calculated SS in 2D materials. More than that, we propose a workflow for materials design integrating an inverse design approach and a Bayesian inference optimization. We use the prediction of SS prototypes for spintronic applications as an illustrative example of the proposed workflow. The prediction process starts with the establishment of the design principles (the physical mechanism behind the target properties), that are used as filters for materials screening, and followed by density functional theory (DFT) calculations. Applying this process to the C2DB database, we identify and classify 358 2D materials according to SS type at the valence and/or conduction bands. The Bayesian optimization captures trends that are used for the rationalized design of 2D materials with the ideal conditions of band gap and SS for potential spintronics applications. Our workflow can be applied to any other material property.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sabino2022b,

title = {Hole conductivity through a defect band in <mml:math xmlns:mml=},

author = {Fernando P. Sabino and Intuon Chatratin and Anderson Janotti and Gustavo M. Dalpian},

url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.6.064602},

doi = {10.1103/physrevmaterials.6.064602},

issn = {2475-9953},

year  = {2022},

date = {2022-06-00},

urldate = {2022-06-00},

journal = {Phys. Rev. Materials},

volume = {6},

number = {6},

publisher = {American Physical Society (APS)},

abstract = {Semiconductors with a wide band gap (>3.0 eV), high dielectric constant (>10), good thermal dissipation, and capable of 𝑛- and 𝑝-type doping are highly desirable for high-energy power electronic devices. Recent studies indicate that ZnGa2⁢O4 may be suitable for these applications, standing out as an alternative to Ga2⁢O3. The simple face-centered-cubic spinel structure of ZnGa2⁢O4 results in isotropic electronic and optical properties, in contrast to the large anisotropic properties of the 𝛽-monoclinic Ga2⁢O3. In addition, ZnGa2⁢O4 has shown, on average, better thermal dissipation and potential for 𝑛- and 𝑝-type conductivity. Here we use density functional theory and hybrid functional calculations to investigate the electronic, optical, and point defect properties of ZnGa2⁢O4, focusing on the possibility for 𝑝- and 𝑛-type conductivity. We find that the cation antisite GaZn is the lowest-energy donor defect that can lead to unintentional 𝑛-type conductivity. The stability of self-trapped holes (small hole polarons) and the high formation energy of acceptor defects make it difficult to achieve 𝑝-type conductivity. However, with an excess of Zn, forming Zn(1+2⁢𝑥)⁢Ga2⁢(1−𝑥)⁢O4 alloys, this compound can display an intermediate valence band, facilitating 𝑝-type conductivity. Due to the localized nature of this intermediate valence band, 𝑝-type conductivity by polaron hopping is expected, explaining the low mobility and low hole density observed in recent experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Caturello2022b,

title = {Pressure-Induced Stabilization of Sodium Halide Perovskites},

author = {Naidel A. M. S. Caturello and Fernando P. Sabino and José A. Souza and Gustavo M. Dalpian},

url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.2c00824},

doi = {10.1021/acs.jpcc.2c00824},

issn = {1932-7455},

year  = {2022},

date = {2022-03-03},

urldate = {2022-03-03},

journal = {J. Phys. Chem. C},

volume = {126},

number = {8},

pages = {4248--4254},

publisher = {American Chemical Society (ACS)},

abstract = {Halide perovskites with the chemical formula ABX3 are promising materials for solar energy harvesting, with their A-site playing an important role in giving stability for the 3D corner-sharing octahedron BX6, forming the perovskite structure. In its inorganic family, the perovskite A-site is usually occupied by Cs, and when lighter atoms such as Na and K are introduced, the perovskite structure becomes unstable compared to other crystal structures. Here, we show that relatively low pressures, ranging from 6.1 to 7.0 GPa, can stabilize Na-based perovskites. We have also found that the band gap energy of these compounds decreases as a function of pressure, revealing a transition from semiconducting to metallic behavior at pressures larger than 50 GPa. These results present a pathway for the stabilization of new perovskites that can be extended to other systems composed of small ions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Acosta2022b,

title = {Machine Learning Study of the Magnetic Ordering in 2D Materials},

author = {Carlos Mera Acosta and Elton Ogoshi and Jose Antonio Souza and Gustavo M. Dalpian},

url = {https://pubs.acs.org/doi/abs/10.1021/acsami.1c21558},

doi = {10.1021/acsami.1c21558},

issn = {1944-8252},

year  = {2022},

date = {2022-02-23},

urldate = {2022-02-23},

journal = {ACS Appl. Mater. Interfaces},

volume = {14},

number = {7},

pages = {9418--9432},

publisher = {American Chemical Society (ACS)},

abstract = {Magnetic materials have been applied in a large variety of technologies, from data storage to quantum devices. The development of two-dimensional (2D) materials has opened new arenas for magnetic compounds, even when classical theories discourage their examination. Here we propose a machine-learning-based strategy to predict and understand magnetic ordering in 2D materials. This strategy couples the prediction of the existence of magnetism in 2D materials using a random forest and the Shapley additive explanations method with material maps defined by atomic features predicting the magnetic ordering (ferromagnetic or antiferromagnetic). While the random forest model predicts magnetism with an accuracy of 86%, the material maps obtained by the sure independence screening and sparsifying method have an accuracy of ∼90% in predicting the magnetic ordering. Our model indicates that 3d transition metals, halides, and structural clusters with regular transition-metal sublattices have a positive contribution in the total weight deciding the existence of magnetism in 2D compounds. This behavior is associated with the competition between crystal field and exchange splitting. The machine learning model also indicates that the atomic spin orbit coupling (SOC) is a determinant feature for the identification of the patterns separating ferro- from antiferromagnetic order. The proposed strategy is used to identify novel 2D magnetic compounds that, together with the fundamental trends in the chemical and structural space, pave novel routes for experimental exploration.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sabino2022,

title = {Intrinsic doping limitations in inorganic lead halide perovskites},

author = {Fernando P. Sabino and Alex Zunger and Gustavo M. Dalpian},

url = {https://pubs.rsc.org/en/content/articlelanding/2021/xx/d1mh01371h/unauth},

doi = {10.1039/d1mh01371h},

issn = {2051-6355},

year  = {2022},

date = {2022-02-07},

urldate = {2022-02-07},

journal = {Mater. Horiz.},

volume = {9},

number = {2},

pages = {791--803},

publisher = {Royal Society of Chemistry (RSC)},

abstract = {Inorganic halide perovskites (HP's) of the CsPbX3 (X = I, Br, Cl) type have reached prominence in photovoltaic solar cell efficiencies, leading to the expectation that they are a new class of semiconductors relative to the traditional ones. Peculiarly, they have shown an asymmetry in their ability to be doped by holes vs. electrons. Indeed, both structural defect-induced doping as well as extrinsic impurity-induced doping strangely often result in HP's in a unipolar doping (dominantly p-type) with low free carriers’ concentration. This raises the question whether such doping limitations presents just a temporary setback due to insufficient optimization of the doping process, or perhaps this represents an intrinsic, physically-mandated bottleneck. In this paper we study three fundamental Design Principles (DP's) for ideal doping, applying them via density functional doping theory to these HP's, thus identifying the violated DP that explains the doping limitations and asymmetry in these HP's. Here, the target DP are: (i) requires that the thermodynamic transition level between different charge states induced by the dopants must ideally be energetically shallow both for donors (n-type) or acceptors (p-type); DP-(ii) requires that the ‘Fermi level pinning energies’ for electrons E(n)pin and holes E(p)pin (being the limiting value of the Fermi level before a structural defect that compensate the doping forms spontaneously) should ideally be located inside the conduction band for n-type doping and inside the valence band for p-type doping. DP-(iii) requires that the doping-induced shift in equilibrium Fermi energy ΔE(n)F towards the conduction band for n-type doping (shift of ΔE(p)F towards the valence band, for p-type doping) to be sufficiently large. We find that, even though in HP's based on Br and Cl there are numerous shallow level dopants that satisfy DP-(i), in contrast DP-(ii) is satisfied only for holes and DP-(iii) fails for both holes and electrons, being the ultimate bottleneck for the n-type doping in Iodide HP's. This suggests an intrinsic mechanism for doping limitations in this class of semiconductors in terms of recognized physical mechanisms.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ferreira2022b,

title = {Introduzindo aprendizado de máquina em cursos de física: o caso do rolamento no plano inclinado},

author = {H. Ferreira and E.F. Almeida Junior and W. Espinosa-García and E. Novais and J.N.B. Rodrigues and Gustavo M. Dalpian},

url = {https://www.scielo.br/j/rbef/a/JS7GjGRH5HmCnqFZSpvFZHK/?lang=pt},

doi = {10.1590/1806-9126-rbef-2022-0214},

issn = {1806-9126},

year  = {2022},

date = {2022-00-00},

urldate = {2022-00-00},

journal = {Rev. Bras. Ensino Fís.},

volume = {44},

publisher = {FapUNIFESP (SciELO)},

abstract = {In an increasingly data-oriented science, the use of automatic computational methods is progressively indispensable. In this context, it becomes important to expose undergraduate physics students to artificial intelligence and machine learning methodologies. In this work we propose a way to use such methods in physics, solving the didactic problem of rolling on an inclined plane. We introduce the main concepts of machine learning techiniques and measure the travel time of different objects (rim, disk and sphere) for an initial height and tilt angle. Based on these data, we used classification models capable of predicting the object that was dropped with an accuracy of 83%, and regression models which were able to predict the average speed of the object that was rolled with mean absolute error of 1.4 cm s−1. We also show that this didactic model is instructive because it allows a direct comparison with physical models and serves as a discussion of the meaning of teaching physics to the computer.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Espinosa-García2021,

title = {Influence of defects on antidoping behavior in <mml:math xmlns:mml=},

author = {W. F. Espinosa-García and Gustavo M. Dalpian},

url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.205106},

doi = {10.1103/physrevb.104.205106},

issn = {2469-9969},

year  = {2021},

date = {2021-11-00},

urldate = {2021-11-00},

journal = {Phys. Rev. B},

volume = {104},

number = {20},

publisher = {American Physical Society (APS)},

abstract = {Samarium nickelate (Sm⁢Ni⁢O3) is a representative quantum material, presenting “exotic” properties including strong correlations and metal-to-insulator transition. It was also shown that Sm⁢Ni⁢O3 presents the unusual antidoping effect, where the resistivity of the material increases with doping instead of decreasing. In this paper, we study intrinsic defects in this compound, and discuss the antidoping behavior in the presence of these defects. Our results show that the negatively charged oxygen vacancy (𝑉−2

O) can be very stable, and the extra electrons move towards the small octahedra (Ni4+ sites), similar to the antidoping effect in the pristine material. This indicates that antidoping should still be observed even in the presence of defects.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{MeraAcosta2021,

title = {Different shapes of spin textures as a journey through the Brillouin zone},

author = {Carlos Mera Acosta and Linding Yuan and Gustavo M. Dalpian and Alex Zunger},

url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.104408},

doi = {10.1103/physrevb.104.104408},

issn = {2469-9969},

year  = {2021},

date = {2021-09-00},

urldate = {2021-09-00},

journal = {Phys. Rev. B},

volume = {104},

number = {10},

publisher = {American Physical Society (APS)},

abstract = {Crystallographic point group symmetry (CPGS) such as polar and nonpolar crystal classes have long been known to classify compounds that have spin-orbit-induced spin splitting. While taking a journey through the Brillouin zone (BZ) from one 𝑘-point to another for a fixed CPGS, it is expected that the wave vector point group symmetry (WPGS) can change, and consequently, a qualitative change in the texture of the spin polarization can occur [the expectation value of spin operator 

⃗

𝑆

𝑛⁢𝑘0 in Bloch state 𝑢⁡(𝑛,𝑘) and the wave vector 𝑘0]. However, the nature of the spin texture (ST) change is generally unsuspected. In this paper, we determine a full classification of the linear-in-𝑘 ST patterns based on the polarity and chirality reflected in the WPGS at 𝑘0. The spin-polarization vector 

⃗

𝑆

𝑛⁢𝑘0 controlling the ST is bound to be parallel to the rotation axis and perpendicular to the mirror planes, and hence, symmetry operation types in WPGSs impose symmetry restriction to the ST. For instance, the ST is always parallel to the wave vector 𝑘 in nonpolar chiral WPGSs since they contain only rotational symmetries. Some consequences of the ST classification based on the symmetry operations in the WPGS include the observation of ST patterns that are unexpected according to the symmetry of the crystal. For example, it is usually established that spin-momentum locking effect (spin vector always perpendicular to the wave vector) requires the crystal inversion symmetry breaking by an asymmetric electric potential. However, we find that polar WPGS can have this effect even in compounds without electric dipoles or external electric fields. We use the determined relation between WPGS and ST as a design principle to select compounds with multiple STs near band edges at different 𝑘 valleys. Based on high-throughput calculations for 1481 compounds, we find 37 previously fabricated materials with different STs near band edges. The ST classification as well as the predicted compounds with multiple STs can be a platform for potential application for spin-valleytronics and the control of the ST by accessing different valleys.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bonadio2021f,

title = {Tailoring the Optical, Electronic, and Magnetic Properties of MAPbI3 through Self-Assembled Fe Incorporation},

author = {A. Bonadio and F. P. Sabino and A. Tofanello and A. L. M. Freitas and V. G. de Paula and Gustavo M. Dalpian and J. A. Souza},

url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.1c03955},

doi = {10.1021/acs.jpcc.1c03955},

issn = {1932-7455},

year  = {2021},

date = {2021-07-22},

urldate = {2021-07-22},

journal = {J. Phys. Chem. C},

volume = {125},

number = {28},

pages = {15636--15646},

publisher = {American Chemical Society (ACS)},

abstract = {We have produced Fe-doped paramagnetic MAPbI3 microwires by using a novel strategy involving a self-assembly growth process of [PbI6]4– octahedral chains in the presence of liquid water. Structural and morphological studies confirmed that after the dissociation and recrystallization process, the doped samples preserved both the perovskite structure with a tetragonal phase and a microwire shape, while X-ray photoelectron spectroscopy revealed the presence of mixed-valence Fe3+/Fe2+ ions with negligible change in the PbI6 cage environment and the maximum valence band position. From first-principles calculations, we determined that Fe2+ ions are localized in the interstitial site while Fe3+ ones are substitutional on Pb sites. The very high mobility and static dielectric constant, achieved by photogenerated charge carriers in MAPbI3, are suppressed for Fe-doped MAPbI3 samples. These results are discussed based on a nonradiative recombination process assisted by phonons that is activated by the inclusion of the Fe ions. Our ab initio calculations support this model that can be also used to explain the quenching of the photoluminescence emission peaks. The successful insertion of dopants that can tune the perovskite’s physical properties is important to the development of functional devices and is also able to open new potential applications such as in magnetic/semiconducting devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bae2021,

title = {MXene Phase with C3 Structure Unit: A Family of 2D Electrides},

author = {Soungmin Bae and William Espinosa‐García and Yoon‐Gu Kang and Noriyuki Egawa and Juho Lee and Kazuaki Kuwahata and Mohammad Khazaei and Kaoru Ohno and Yong‐Hoon Kim and Myung Joon Han and Hideo Hosono and Gustavo M. Dalpian and Hannes Raebiger},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202100009},

doi = {10.1002/adfm.202100009},

issn = {1616-3028},

year  = {2021},

date = {2021-06-00},

urldate = {2021-06-00},

journal = {Adv Funct Materials},

volume = {31},

number = {24},

publisher = {Wiley},

abstract = {A new structural phase is discovered for M2CO2 MXenes with M = Sc, Y, La, Lu, Tm, and Ho. The hexagonal carbon layer sandwiched between M atoms, typical for MXenes, is transformed into C3 trimers with anionic electrons localized in quasi zero-dimensional lattice spaces in-between the C3 units, so the systems can be described as [M6 C3 O6]+II : 2e− electrides. The systems are readily ionized into [M6 C3 O6]+II with very low ionization energy via an anti-doping mechanism. It is shown that this new structure of Sc2CO2 can bind multiple lithium atoms, with low migration barriers. The findings indicate that these M2CO2 MXenes with unusual carbon trimers are a new family of 2D electride insulators with the potential for charge storage applications, thermal field emission, and as anode material in lithium batteries.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{NegreirosRibeiro2021,

title = {\textit{Ab initio} atomistic description of temperature-induced phase changes: The cases of zirconia and Ti-Y-co-doped zirconia},

author = {Fabio Negreiros Ribeiro and Dolores Ribeiro Ricci Lazar and Valter Ussui and Nelson Batista de Lima and Juliana Marchi and Gustavo M. Dalpian},

url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.5.023603},

doi = {10.1103/physrevmaterials.5.023603},

issn = {2475-9953},

year  = {2021},

date = {2021-02-00},

urldate = {2021-02-00},

journal = {Phys. Rev. Materials},

volume = {5},

number = {2},

publisher = {American Physical Society (APS)},

abstract = {Zirconium dioxide, or zirconia, is a common and useful ceramic with a wide range of applications, from fuel cells to odontology. Its phase diagram is simple and well understood, having a structure which is monoclinic at temperatures up to 1500 K, tetragonal up to 2700 K and cubic up to 3000 K. Zirconia is rarely used in its pure form, being typically doped with Y2⁢O3, MgO or TiO2, and in this regime its phase diagram becomes much more complex. In this context, ab initio molecular dynamics (AIMD) can provide a detailed atomistic description of the phase diagram of this system, accurately describing its stable phases and transition regions. In this work, 3 mol-% Y2⁢O3 (3YSZ) crystals doped with different Ti contents were studied at the density-functional level. For Ti contents varying from 0 to 30 at%, a global search algorithm was first used to explore the 0 K potential-energy surface and determine the most stable sites for the added Ti atoms. It was found that, at low Ti compositions 𝑋Ti, small TiO2 clusters form, followed by TiO2 channels and infinite TiO2 planes at larger 𝑋Ti values, and that the highest stability is achieved at 9% Ti. AIMD simulations within the isothermal-isobaric NPT ensemble were then performed to characterize the temperature-dependent phase changes as a function of the Ti content, where it was found that the Ti-doped structures presented considerably smaller volume changes near the phase-change critical temperatures. These findings suggest that YSZ materials doped with a small amount of Ti are both energetically and kinetically more stable than the undoped counterparts, in the ideal proportion of 3% TiO2 for every 1% Y2⁢O3 doping.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bonadio2021e,

title = {Entropy-driven stabilization of the cubic phase of MaPbI3 at room temperature},

author = {A. Bonadio and C. A. Escanhoela and F. P. Sabino and G. Sombrio and V. G. de Paula and F. F. Ferreira and A. Janotti and Gustavo M. Dalpian and J. A. Souza},

url = {https://pubs.rsc.org/en/content/articlehtml/2021/ta/d0ta10492b},

doi = {10.1039/d0ta10492b},

issn = {2050-7496},

year  = {2021},

date = {2021-01-19},

urldate = {2021-01-19},

journal = {J. Mater. Chem. A},

volume = {9},

number = {2},

pages = {1089--1099},

publisher = {Royal Society of Chemistry (RSC)},

abstract = {Methylammonium lead iodide (MAPbI3) is an important light-harvesting semiconducting material for solar-cell devices. We investigate the effect of long thermal annealing in an inert atmosphere of compacted MAPbI3 perovskite powders. The microstructure morphology of the MAPbI3 annealed samples reveals a well-defined grain boundary morphology. The voids and neck-connecting grains are observed throughout the samples, indicating a well-sintered process due to mass diffusion transfer through the grain boundary. The long 40 h thermal annealing at T = 522 K (kBT = 45 meV) causes a significant shift in the structural phase transition, stabilizing the low-electrical conductivity and high-efficiency cubic structure at room temperature. The complete disordered orientation of MA cations maximizes the entropy of the system, which, in turn, increases the Pb–I–Pb angle close to 180°. The MA rotation barrier and entropy analysis determined through DFT calculations suggest that the configurational entropy is a function of the annealing time. The disordered organic molecules are quenched and become kinetically trapped in the cubic phase down to room temperature. We propose a new phase diagram for this important system combining different structural phases as a function of temperature with annealing time for MAPbI3. The absence of the coexistence of different structural phases, leading to thermal hysteresis, can significantly improve the electrical properties of the solar cell devices. Through an entropy-driven stabilization phenomenon, we offer an alternative path for improving the maintenance, toughness, and efficiency of the optoelectronic devices by removing the microstructural stress brought by the structural phase transformation within the solar cell working temperature range.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}