Functional designed to include surface effects in self-consistent density functional theory

Abstract

We design a density-functional-theory (DFT) exchange-correlation functional that enables an accurate treatment of systems with electronic surfaces. Surface-specific approximations for both exchange and correlation energies are developed. A subsystem functional approach is then used: an interpolation index combines the surface functional with a functional for interior regions. When the local density approximation is used in the interior, the result is a straightforward functional for use in self-consistent DFT. The functional is validated for two metals (Al, Pt) and one semiconductor (Si) by calculations of (i) established bulk properties (lattice constants and bulk moduli) and (ii) a property where surface effects exist (the vacancy formation energy). Good and coherent results indicate that this functional may serve well as a universal first choice for solid-state systems and that yet improved functionals can be constructed by this approach

Reactive force field simulation of proton diffusion in BaZrO3using an empirical valence bond approach

“…For the current work we employ one of a number of recent GGA functionals that appear to offer superior results for condensed phases. In particular, we choose to use the AM05 functional [24], which has been demonstrated to give good results for lattice parameters, the relative energies of polymorphs [25] and, importantly when considering proton incorporation, even water clusters [26].…”

Self-consistent meta-generalized gradient approximation within the projector-augmented-wave method

“…Since the commonly used GGAs in general overcorrect the lattice constant with respect to LSDA, recent years have seen the emergence of "GGAs for solids" with diminished gradient dependences (e.g., AM05 18 and PBEsol 19 ) which typically predict good lattice constants and surface energies, but rather poor atomization energies.…”

The small unit cell reconstructions of SrTiO3(111)

“…The most common functional used is the PBE GGA [14], which while it often gives very good results, still has some problems particularly for energies. For instance, it is now well established that it severely underestimates surface energies [20][21][22]. In addition, for many bulk transition element oxides there is too much hybridization between the metal 3d-electrons and the oxygen 2sp, and the classic method for correcting this is what has become known as the LDA+U method [23,24].…”

“…As mentioned above, the PBE functional gives poor surface energies. A much better method for this is the TPSS meta-GGA functional [18] which includes beside the gradient of the density also the kinetic energy-density in the functional form which is known to match quite well the long-range jellium surface energies which are believed to be an issue with PBE [20][21][22]. TPSS also gives much better atomization energies for molecules.…”