Banca de QUALIFICAÇÃO: RICARDO GOMES

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: RICARDO GOMES
DATA: 28/08/2026
HORA: 14:00
LOCAL: Remota
TÍTULO: INFLUÊNCIA DA HIDRATAÇÃO NAS PROPRIEDADES ESTRUTURAIS, ELETRÔNICAS, ÓPTICAS, VIBRACIONAIS E TERMODINÂMICAS DE ÓXIDOS DE TUNGSTÊNIO: UM ESTUDO VIA DFT
PALAVRAS-CHAVES: hydrated tungsten oxides; DFT; HSE06; electronic structure; vibrational spectroscopy.
PÁGINAS: 61
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
RESUMO:

Tungsten trioxide (WO₃) is a transition-metal oxide that exhibits different crystalline phases and
electronic, optical, and vibrational properties of interest for applications in electrochromic devices,
sensors, photocatalysis, and energy conversion. The incorporation of water into the crystal lattice
can significantly modify the local atomic coordination, electronic structure, and vibrational
dynamics of the material. In this work, the structural, electronic, optical, vibrational, and
thermodynamic properties of anhydrous and hydrated tungsten oxide phases were investigated
through a combined approach involving experimental characterization and first-principles
calculations based on Density Functional Theory (DFT). The calculations were performed using the
CASTEP code, employing the GGA-PBE functional for structural optimizations and determination
of physical properties, as well as the HSE06 hybrid functional for a more accurate description of the
electronic structure, applied exclusively to the anhydrous O-WO₃ phase. X-ray diffraction results
confirmed the formation of the investigated orthorhombic phases and revealed anisotropic changes
in the lattice parameters associated with hydration. Electronic band-structure calculations indicated
semiconducting behavior for both structures, with band gaps of 0.904 eV and 2.848 eV obtained for
orthorhombic WO₃ using GGA-PBE and HSE06, respectively, whereas the hydrated phase
exhibited a band gap of 1.499 eV at the GGA-PBE level. PDOS analysis showed that the valence-
band edge is predominantly composed of O-2p states, while the conduction band exhibits a strong
contribution from W-5d states. Optical calculations revealed an anisotropic response and hydration-
induced changes in the absorption and reflectivity spectra. The calculated Raman and infrared
spectra reproduced the main vibrational features of the W–O framework and identified high-
frequency modes associated with O–H bonds in the hydrated structure. Thermodynamic properties
derived from vibrational contributions revealed differences in entropy, free energy, and heat
capacity arising from the additional degrees of freedom introduced by hydration.

MEMBROS DA BANCA:
Presidente - 2056226 - CLEANIO DA LUZ LIMA
Externo ao Programa - 689.***.***-04 - EDIOMAR COSTA SERRA - UEMA
Externo ao Programa - 049.***.***-93 - EDUILY BENVINDO VAZ FREIRE - UFS
Interno - 1720015 - GARDENIA DE SOUSA PINHEIRO