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.