<i>Ab initio</i>multicenter tight-binding model for molecular-dynamics simulations and other applications in covalent systems

TLDR

The authors develop an approximate method to compute total energies and forces for covalent materials, enabling molecular‑dynamics simulations. The method is a tight‑binding‑like model derived from density‑functional theory with pseudopotentials, using slightly excited pseudo‑atomic orbitals to construct a real‑space Hamiltonian for electronic structure calculations. The approach yields excellent agreement with experiment and other first‑principles methods, and successfully predicts the ground‑state configuration of Si₃ and the spectral density of Si₂ across excitation levels.

Abstract

A new, approximate method has been developed for computing total energies and forces for a variety of applications including molecular-dynamics simulations of covalent materials. The method is tight-binding-like and is founded on density-functional theory within the pseudopotential scheme. Slightly excited pseudo-atomic-orbitals are used to derive the tight-binding Hamiltonian matrix in real space. The method is used to find the electronic states and total energies for a variety of crystalline phases of Si and the ${\mathrm{Si}}_{2}$ molecule. Excellent agreement is found with experiment and other first-principles methods. As simple applications of the method, we perform a molecular-dynamics simulated-annealing study of the ${\mathrm{Si}}_{3}$ molecule to determine the ground-state configuration, and a molecular-dynamics simulation of the spectral density function of the ${\mathrm{Si}}_{2}$ molecule at high and low excitation levels.