DFT Calculations of the Structural, Electronic, Optical and Vibrational Properties of Anhydrous Orthorhombic L-Threonine Crystals

Publication date: Available online 21 October 2019Source: Computational and Theoretical ChemistryAuthor(s): Roniel L. Araújo, Manoel S. Vasconcelos, Carlos A. Barboza, José X. Lima Neto, Eudenilson L. Albuquerque, Umberto L. FulcoAbstractThe 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 Δa,Δb,Δc of -0.08 Å, 0.12 Å, and 0.01 Å, 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.Graphical abstract

Source: Computational and Theoretical Chemistry - October 22, 2019 Category: Chemistry Source Type: research