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

Abstract

AbstractThe performance of 12 DFT functionals in describing the equilibrium structure and the relative stability of three Al2SiO5 orthosilicates (kyanite, andalusite and sillimanite) and four Al2O3 · nH2O 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 Al2SiO5 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 range of stability but they are often unsatisfactory in reproducing the correct order of stability. This is particularly relevant for the B3LYP functionals. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010