Professor Gustavo Dalpian

@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 = {2024-02-29},

urldate = {2024-12-00},

journal = {Discov Mater},

volume = {4},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractHaving 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 = {General Medicine},

pubstate = {published},

tppubtype = {article}

}

@article{Ogoshi2024b,

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://repositorio.usp.br/directbitstream/1ee44f9f-13de-45ad-bb4b-fb7f0cb95272/3183025%20falta%20rep.pdf},

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

issn = {2730-7727},

year  = {2024},

date = {2024-02-29},

urldate = {2024-12-00},

journal = {Discov Mater},

volume = {4},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractHaving 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 = {General Medicine},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1021/acsami.3c16541,

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://doi.org/10.1021/acsami.3c16541},

doi = {10.1021/acsami.3c16541},

year  = {2024},

date = {2024-01-13},

journal = {ACS Applied Materials & Interfaces},

volume = {0},

number = {0},

pages = {null},

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.},

note = {PMID: 38217498},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/aenm.202301539,

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 = {https://doi.org/10.1002/aenm.202301539},

year  = {2023},

date = {2023-10-11},

journal = {Advanced Energy Materials},

volume = {n/a},

number = {n/a},

pages = {2301539},

abstract = {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 = {Alloys of halide perovskite, Frenkel pair, Phase segregation},

pubstate = {published},

tppubtype = {article}

}

@article{ESPINOSAGARCIA2023172264,

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/pii/S0925838823035673},

doi = {https://doi.org/10.1016/j.jallcom.2023.172264},

issn = {0925-8388},

year  = {2023},

date = {2023-09-25},

urldate = {2023-01-01},

journal = {Journal of Alloys and Compounds},

pages = {172264},

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 for understanding the search for ways to design and tune the properties of these compounds.},

keywords = {Defects, First-principles calculations, P-type materials, Semiconductors, Sulvanite},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1021/acs.inorgchem.3c00874,

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://doi.org/10.1021/acs.inorgchem.3c00874},

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

year  = {2023},

date = {2023-01-01},

journal = {Inorganic Chemistry},

volume = {62},

number = {19},

pages = {7533-7544},

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.},

note = {PMID: 37126785},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{YADAV20232711,

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.sciencedirect.com/science/article/pii/S2590238523002370},

doi = {https://doi.org/10.1016/j.matt.2023.05.019},

issn = {2590-2385},

year  = {2023},

date = {2023-01-01},

journal = {Matter},

volume = {6},

number = {9},

pages = {2711-2734},

abstract = {Summary 

The successful exfoliation of graphene from graphite has brought significant attention to predicting new two-dimensional (2D) materials that can be realized experimentally. As a consequence, first-principles studies of novel 2D materials become routine, with thousands of papers published every year. What makes these studies interesting is that they predict new materials that have not been realized yet but should be a panacea for topological insulators, next-generation battery electrodes, novel solar cell absorbers, etc. There is no doubt that some of the proposed materials can provide a specific solution, and their properties/performance can be confirmed experimentally. At the same time, there are many false predictions because of the computational errors or the Legoland approach used to study 2D materials. To reduce the gap between theoretical and experimental works, we performed a systematic review of computational and Legoland factors that should be minimized in future theoretical works.},

keywords = {2D materials, materials design, materials realization, optical properties},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1021/acsanm.3c00242,

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://doi.org/10.1021/acsanm.3c00242},

doi = {10.1021/acsanm.3c00242},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {ACS Applied Nano Materials},

volume = {6},

number = {9},

pages = {7196-7205},

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{BEZZON2023136412,

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

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

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

doi = {https://doi.org/10.1016/j.molstruc.2023.136412},

issn = {0022-2860},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {Journal of Molecular Structure},

volume = {1294},

pages = {136412},

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 = {Doxorubicin hydrochloride, Powder X-ray diffraction, Rietveld refinement, Simulated annealing approach},

pubstate = {published},

tppubtype = {article}

}

@article{Ussui2022,

title = {Room temperature plasticity of zirconia-yttria-titania ceramics: Experimental indications and structural modelling},

author = {Valter Ussui and Dolores Ribeiro Lazar and Nelson de Lima and Anelyse Arata and Fabio Ribeiro and Gustavo M. Dalpian and Juliana Marchi and José Octavio Paschoal},

doi = {10.2298/pac2204367u},

issn = {2406-1034},

year  = {2023},

date = {2023-00-00},

urldate = {2023-00-00},

journal = {PAC},

volume = {16},

number = {4},

pages = {367--373},

publisher = {National Library of Serbia},

abstract = {Yttria-stabilized tetragonal zirconia (Y-TZP) ceramics have excellent

   mechanical properties. However, such materials cannot undergo plastic

   deformation at room temperature due to their high hardness and brittleness

   values, hindering machinability. To overcome these limitations, we propose a

   zirconia-yttria-titania ceramics, based on zirconia containing 3mol% yttria

   and up to 15mol% titania. The zirconia-yttria-titania powders were

   synthesized by co-precipitation method, uniaxially pressed and sintered at

   1400?C/5 h. Sample characterizations were carried out by X-ray diffraction,

   scanning electron microscopy and mechanical properties through Vickers

   hardness and toughness measurements. Compared to the Y-TZP ceramics, the

   yttria stabilised tetragonal zirconia ceramics co-doped with 10mol%Ti showed

   noticeable increase of tetragonality parameter, higher toughness and lower

   hardness values, indicating plasticity at room temperature. Furthermore, the

   atomistic simulation by Density Functional Theory methodology suggests the

   occurrence of spatial arrangement of the atoms, explaining the proposed

   plasticity.},

keywords = {Ceramics and Composites},

pubstate = {published},

tppubtype = {article}

}