Performance of 12 DFT functionals in the study of crystal systems: Al₂SiO₅ orthosilicates and Al hydroxides as a case study

Abstract

ABSTRACT:The performance of 12 DFT functionals in describing the equilibrium structure and the relative stability of three Al 2 SiO 5 orthosilicates (kyanite, andalusite and sillimanite) and four Al 2 O 3 · nH 2 O hydroxides (diaspore, boehmite, gibbsite, and bayerite, with the last three systems being H-bonded layered structures, HBLs) is assessed. Calculations were performed with the periodic ab initio CRYSTAL code by using all electron Gaussian-type basis sets. The exchange-correlation functionals tested are: Two LDA functionals (SVWN and PWLSD), five semilocal GGA functionals, both the standard ones tailored for molecules (PW and PBE) and the newly functionals devised for solids (PBEsol, SOGGA, and WC), and five hybrid functionals (B1WC, WC1LYP, B3LYP, B3PW, and PBE0). We find that recent GGA functionals for solids give similar results that are in between LDA and standard GGA functionals. They reproduce quite well the structure of Al 2 SiO 5 polymorphs but fail for the H-bonded layered Al hydroxides. The inclusion of HF exchange in the hybrid functionals leads to very good predicted structures for both systems. In particular, the structural parameters related to H atoms (OH and H· · · O distances, the lattice parameter along which the layers are stacked in HBLs) are remarkably improved with respect to the LDA and GGA functionals. Among the studied polymorphs, the correct order of stability is obtained with LDA and GGA functionals for solids, even if they overstabilize denser phases. Standard GGA and hybrids reduce the PERFORMANCE OF 12 DFT FUNCTIONALSrange of stability but they are often unsatisfactory in reproducing the correct order of stability. This is particularly relevant for the B3LYP functionals.

Cryscor: a program for the post-Hartree–Fock treatment of periodic systems

“…Yet it has been demonstrated in ref. 71, that all but the electronic contributions are expected to affect the computed relative stability at most by 2-3 kJ mol…”

“…Table 2 and ref. 71). However, the relative stability of these systems is of great interest in the context of simulations of geological processes.…”

Thermodynamics and phonon dispersion of pyrope and grossular silicate garnets from ab initio simulations

“…This can be related to the well known fact that the B3LYP functional, despite its excellent overall behavior in reproducing vibrational spectra of solids, undershoots systematically low wavenumbers, roughly those below 150 cm −1 (Demichelis et al 2010b;De La Pierre et al 2011;Maschio et al 2011;Dovesi et al 2011;Maul et al 2015). Indeed, common experience with B3LYP shows that this Hamiltonian describes softer structures with respect to reality, (Demichelis et al 2010a) overestimating the lattice parameters. Table S3 of the Supplementary Information shows that also in the case of pyrope the agreement with experimental spectra is quite good, with an overall slight underestimation of the frequencies (∆ ν=-1.3 cm −1 ) and a mean absolute error (MAE) of 5.7 cm −1 .…”

Electron correlation decides the stability of cubic versus hexagonal boron nitride

“…The notorious inability of standard DFT to describe the long-range correlation effects in fact hinders the possibility to capture the correct physics in extended systems, especially so when weak binding is involved. A serious warning about the reliability of DFT techniques in predicting the relative stability of crystalline allotropes comes from a recent study by Demichelis et al 24 Within the same computational scheme, the performance of 12 DFT functionals was there assessed as concerns the equilibrium structure and the relative stability of three aluminosilicates and four aluminum hydroxides. Without entering into details, the results were shown to depend strongly on the exchange-correlation functional used.…”