hide
Free keywords:
carbon materials; electronic structure; ab initio calculations; tight-binding; transferability
Abstract:
The third-generation LMTO method provides a new wave function
basis set in which the energy dependence of the interstitial
region and inside muffin-tin (MT) spheres is treated on an
equal footing. Within the improved method, basis functions in
the interstitial are the screened spherical waves (SSWs) with
boundary condition defined in terms of a set of 'hard' sphere
radii a(RL). Energy eigenvalues obtained from the single-
particle Schrodinger equation for MT potential is energetically
accurate and very useful for predicting a reliable first-
principles tight-binding (TB) model of widely different
systems. In this study, we investigate a possibility of the new
basis sets transferability to different environment which could
be crucial for TB applications to very large and complicated
systems in realistic materials modelling. For the case of C
where the issue of sp(2) vs sp(3) bonding description is
primarily important, we have found that by downfolding the
unwanted channels in the basis, the TB electronic structure
calculations in both hexagonal graphite and diamond structures
are well compared with those obtained from the full LDA schemes
if we use the same choice of hard sphere radii, a(RL) and a
fixed, arbitrary energy, epsilon(v) Moreover, the choice is
robust and transferable to various situations, from different
forms of graphite to a wide range of coordination. Using the
obtained minimal basis set, we have been investigating the TB
Hamiltonian and overlap matrices for different structure types
for carbon, in particular we have predicted the on-site and
hopping parameters (gamma1, gamma2,...,gamma6) within an
orthogonal representation for Slonczewski-Weiss-McClure (SWMcC)
model of the Bernal structure. Our theoretical values are in
excellent agreement with experimental ones from
magnetoreflection measurements of Fermi surfaces for hexagonal
graphite.
