Simulation of Structural Evolution Using Time-Dependent Density-Functional Based Tight-Binding Method.

ABSTRACT

A faster and more efficient quantum mechanical simulation method for application to complicated issues of real systems beyond model cases has long been sought after. The density-functional based tight-binding (DFTB) method has successfully explained the atomistic and electronic properties of semiconductors, surfaces, and nanostructures. In addition, the time-dependent formalism implemented in DFTB showed high efficiency in terms of computational cost. In this study, we demonstrated the structural and electronic evolution of small molecules induced by a laser pulse using the time-dependent DFTB (TD-DFTB) method. We identified the critical fluence of the input laser for structural dissociations in carbon chains and fullerenes, which related to the structural stability. The excitation energies of several molecules calculated by TD-DFTB agreed with the experimental values.