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

Instituto de Qui ´mica Fisica Rocasolano, CSIC, Serrano 119, E-28006 Madrid, Spain~Received 10 November 1999!A recently proposed tight-binding Hamiltonian model for Selenium @Phys. Rev. B 60, 6372 ~1999!# ismodified to incorporate the effect of charge-charge correlations via an empirical Hubbard contribution. Thecorrection term is fitted to reproduce the cohesive energy curve of a finite chain structure while retaining thequality of the tight-binding fit for various rings, infinite chains, and solid phases. The Hubbard corrections areincorporated in the Hellman-Feynman forces via a first-order perturbation theory. The structure and dynamicsof 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 thecharge-transfer minimization. This translates into a better agreement withab initio simulation data and experi-mental evidence, which also reflects in improved estimates for the bond angle distribution functions and theelectronic band structure. On the other hand, the pair distribution function and the atomic structure factor arehardly affected by the Hubbard corrections. The minimization of charge transfer brings about the stabilizationof longer chains and consequently the microscopic dynamics is also affected, showing both a decrease of thediffusion coefficients and an increase of the bond-stretching band in the vibrational spectrum.I. INTRODUCTION