Hubbard corrections in a tight-binding Hamiltonian for Se: Effects on the band structure, local order, and dynamics

Abstract

A recently proposed tight-binding Hamiltonian model for Selenium ͓Phys. Rev. B 60, 6372 ͑1999͔͒ is modified to incorporate the effect of charge-charge correlations via an empirical Hubbard contribution. The correction term is fitted to reproduce the cohesive energy curve of a finite chain structure while retaining the quality of the tight-binding fit for various rings, infinite chains, and solid phases. The Hubbard corrections are incorporated in the Hellman-Feynman forces via a first-order perturbation theory. The structure and dynamics of various thermodynamics states, obtained from molecular-dynamic simulations in the canonical ensemble, evidence a marked decrease in the number of threefold and onefold defects in the Se chains as a result of the charge-transfer minimization. This translates into a better agreement with ab initio simulation data and experimental evidence, which also reflects in improved estimates for the bond angle distribution functions and the electronic band structure. On the other hand, the pair distribution function and the atomic structure factor are hardly affected by the Hubbard corrections. The minimization of charge transfer brings about the stabilization of longer chains and consequently the microscopic dynamics is also affected, showing both a decrease of the diffusion coefficients and an increase of the bond-stretching band in the vibrational spectrum.

Photo-induced volume changes in selenium. Tight-binding molecular dynamics study

“…For calculating the inter-atomic forces in a-Se we used tight-binding (TB) [9] and self-consistent tight-binding (SCF-TB) [10] models. The TB parametrization [9] has been introduced for disordered selenium following the techniques developed by Goodwin et al [11].…”

Photoinduced volume changes in obliquely deposited a‐Se

“…To study the photoinduced structural changes in these amorphous samples further MD simulations were ran using a TB model Hamiltonian [14]. This TBMD computer code was developed by Hegedüs et al [9,15].…”

Universal feature of photo-induced volume changes in chalcogenide glasses

“…Self-consistency was taken into account via the on-site Hubbard term within the TB model [14,15]. We used the velocity Verlet algorithm to follow the motion of atoms with a time step equals to Dt = 2 fs.…”