10.1021/acs.cgd.0c00489.s001 Neubi Francisco Xavier Neubi Francisco Xavier Antônio Marques da Silva Antônio Marques da Silva Glauco F. Bauerfeldt Glauco F. Bauerfeldt What Rules the Relative Stability of α‑, β‑, and γ‑Glycine Polymorphs? American Chemical Society 2020 298.15 K band structure calculations α- glycine phase transition temperature mol D 3 dispersion correction PBE band gap values γ- glycine 1 bar parameter 2020-05-23 03:43:19 Journal contribution https://acs.figshare.com/articles/journal_contribution/What_Rules_the_Relative_Stability_of__and_Glycine_Polymorphs_/12361241 Theoretical calculations based on the density functional theory, using the PBE functional with the D3 dispersion correction under periodic boundary conditions, have been employed aiming to investigate the properties of α-, β-, and γ-glycine. Structural parameters have been predicted with a maximum error of 1.42% for lattice parameters and 2.53% for the unit-cell volume, for the α phase. Band structure calculations suggest the band gap values of 4.80, 5.01, and 5.23 eV for the α, β, and γ phases, respectively. Quasi-harmonic calculations have been performed and the Gibbs free energy function has been calculated in a wide range of temperature and pressures, suggesting the stability ordering γ > α > β, at room temperature, and the γ to α-glycine phase transition temperature of 442.55 K, at 1 bar, in agreement with the experimental findings. Moreover, a deviation from the experimental value of only 0.44 J mol<sup>–1</sup> K<sup>–1</sup> is observed for the predicted S<sub>(α→γ)</sub> at 298.15 K. Finally, calculated sublimation enthalpies of 140.58, 138.09, and 141.70 kJ mol<sup>–1</sup> (α, β, and γ-glycine, respectively), at 298.15 K and 1 bar, have also shown good agreement with the experimental values.