Optimized and transferable nonlocal separableab initiopseudopotentials

Abstract

The purpose of the present work is to obtain a better atomic pseudopotential with respect to convergence and computational eSciency while retaining reasonable transferability in the context of electronic-structure calculations for solids using a plane-wave basis set. We introduce a systematic procedure for generating optimized nonlocal pseudopotentials by minimizing the high Fourier components of the pseudo-wave-functions with the constraints of normalization and continuity of first and second derivatives of the wave function at the core radius. This is based on the recent ideas of Rappe et al. (RRKJ) [Phys. Rev. B 41, 1227(1990],but overcomes certain difficulties which we have found with the RRKJ scheme. For computational efficiency this optimized nonlocal pseudopotential is transformed into a Kleinman-Bylander (KB) form. To ensure the transferability we first compare the logarithmic derivative of the all-electron wave function with that of the final KB form of the optimized nonlocal pseudopotential over a wide range of energies. We then test the KB form of the potential in a number of atomic environments.The structural properties of ZnS are calculated to demonstrate the reliability of our optimized nonlocal separable ab initio pseudopotential and its total-energy convergence.

Beryllium-free Li4Sr(BO3)2 for deep-ultraviolet nonlinear optical applications

“…The first-principles calculations for the electronic structures in Li 4 Sr(BO 3 ) 2 were performed by the plane-wave pseudopotential method implemented in the CASTEP package based on the density functional theory [27][28][29] . The ion-electron interactions were modelled by the optimized normalconserving pseudopotentials 41 and the local density approximation 27 was chosen for all the calculations. The kinetic energy cutoff of 900 eV and the MonkhorstPack k-point meshes 42 with a density of (4 Â 4 Â 2) points in the Brillouin zone were adopted.…”

First-principles calculations of2×2reconstructions of GaN(0001) surfaces involving N, Al, Ga, In, and As atoms

“…The DFT surface calculations carried out made use of the CASTEP code 19 using the generalized gradient approximation ͑GGA͒ of Perdew and Wang ͑PW91͒. 20 The ions are described by norm-conserving, nonlocal atomic pseudopotentials in the Kleinman-Bylander form generated using the optimization scheme of Lin et al, 21 except in the case of the In atom, where the ultrasoft pseudopotential proposed by Vanderbilt 22 has been used. The Ga 3d states are included within the valence band because of the demonstrable improvements in structural properties and enthalpy of formation.…”

Properties of Complex Inorganic Solids

“…The total energy code CASTEP (MSI 1998) was used, which utilises pseudopotentials to describe electron-ion interactions and represents electronic wavefunctions using a plane wave basis set (Payne et al 1992). We used ultrasoft pseudopotentials (Vanderbilt 1990) which require significantly less computational resources than norm-conserving potentials (Lin et al 1993). The density mixing scheme as described by Kresse and Furthmiiller (1996) was used for self-consistent solution of the density functional equations.…”