Banca de QUALIFICAÇÃO: ALEXANDRE OLIVIERI KRAUS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : ALEXANDRE OLIVIERI KRAUS
DATA : 06/11/2020
HORA: 14:00
LOCAL: por participação remota: https://conferenciaweb.rnp.br/webconf/sydney
TÍTULO:

Vacancy effects on Orthorhombic NaNbO₃ in Bulk and Thin-film Forms: a First-Principles Study

PÁGINAS: 62
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física Atômica e Molecular
ESPECIALIDADE: Estudos de Átomos e Moléculas Especiais
RESUMO:

The conversion of light into chemical bonds through photocatalysis offers a clean route for hydrogen gas production. The fuel production requires that the photocatalyst has electronic bands well aligned with the water-splitting potentials, which can be achieved by inserting defects on the crystal lattice. We investigate the point defect's impact on the orthorhombic NaNbO₃ crystalline and electronic structure with first-principles simulations on bulk and thin-film models. For small concentrations (0.625% at.) in the bulk supercell, both the Na and O neutral vacancies deform their neighborhood, inserting Nb 5d defect states inside the bandgap. The O vacancy partially fills those defect states, nearing the Fermi level to the conduction band as an n-type dopant. The bulk cleavage at the [100] direction forms a NaNbO-terminated thin-film with charge excess. The biaxial strain can modulate both the surface's charge excess and spin modulation. The spin polarization increases (decreases) with the tensile (compressive) strain by raising (lowering) the energetic difference between states with opposite spins. Finally, we propose that the thin-film's introduction of point defects could recover the semiconductor response by rearranging the surface's charge excess. Also, the bandgap values' correction with GW or hybrid potentials permits better comparison with water-splitting potentials, giving an insight into the perovskite's improvement as a photocatalyst.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1671292 - SYDNEY FERREIRA SANTOS
Membro Titular - Examinador(a) Interno ao Programa - 1957564 - CEDRIC ROCHA LEAO
Membro Titular - Examinador(a) Externo ao Programa - 1765425 - MARCIO GUSTAVO DI VERNIERI CUPPARI
Membro Suplente - Examinador(a) Interno ao Programa - 2218228 - LUANA SUCUPIRA PEDROZA
Membro Suplente - Examinador(a) Externo ao Programa - 1282172 - ROBERTO GOMES DE AGUIAR VEIGA