DFT calculations of the structural, electronic, optical and vibrational properties of anhydrous orthorhombic L-threonine crystals

• Autor(a) principal: Araújo, Roniel de Lima
• Data de Publicação: 2019
• Outros Autores: Vasconcelos, Manoel Silva de, Barboza, Carlos Antonio, Lima Neto, José Xavier de, Albuquerque, Eudenilson Lins de, Fulco, Umberto Laino
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/jspui/handle/123456789/29916
• topic: DFT; Anhydrous orthorhombic L-threonine; Electronic properties; Optical properties; Vibrational properties

The structural, electronic, optical, vibrational and thermodynamic properties of the anhydrous orthorhombic L-threonine crystals are investigated by ab initio simulation using a pseudopotential approach within the density functional theory (DFT) method. We have considered both the generalized gradient approximation with dispersion correction (GGA+TS) and the local density approximation (LDA), respectively, as our exchange functionals. Within the GGA+TS calculations, an excellent agreement between the measured X-ray and our theoretical unit cell parameters was obtained, with deviations ∆a, ∆b, ∆c of -0.08 ˚A, 0.12 ˚A, and 0.01 ˚A, respectively, for an 830 eV cutoff energy. Besides, a direct-band gap E(Γ → Γ)=5.06 eV, was found in agreement with the experimental 4.96 eV result. The optical properties have been calculated considering [001] as the incidence direction of polarization of the incident light. The normal vibration’s modes, the infrared and Raman spectra of L-threonine, as well as the thermodynamic properties were also obtained and analyzed