Influence of Electronic Correlation on Structural, Dynamic, and Elastic Properties of Mg2Si

Abstract

A wide variety of ab initio methods are used to study systematically the effects of electronic correlation on the charge density distribution, band structure, lattice parameters, phonon frequencies at the Brillouin zone center, and first-order elastic constants (Cij) of Mg2Si. Two distinct atom-centered basis sets have been used: an all electron one, and another associated with core pseudopotentials. Various levels of approximation have been tested: (i) HF (Hartree−Fock−Roothaan) calculations with no correlation energy correction; (ii) Hartree−Fock plus a posteriori correlation energy correction estimated using various DFT (density functional theory) correlation functionals applied to the Hartree−Fock electronic density; (iii) DFT calculations with “exact” HF exchange and various DFT correlation functionals; (iv) “complete” DFT calculations in which both exchange and correlation are treated using a selection of exchange-correlation functionals. On the ground of a comparison of the numerous data, complem...