Parametrization scheme with accuracy and transferability for tight-binding electronic structure calculations with extended Hückel approximation and molecular dynamics simulations

A transferable tight-binding parametrization procedure for extended Hückel approximation is proposed, with the charge self-consistent scheme, that could be applied to the quantum molecular dynamics (MD) simulation for long-time dynamics of large-scale systems. In this procedure, either a target molecule is divided into small molecules or another realistic set of small molecules characterizing chemical bonds in the complicated target molecule is adopted. Then, the parameters for these small molecules are adjusted and compared with reference results of energy levels and wave functions by, for example, density functional theory. Upon application to the large target molecule, these parameters are then readjusted directly in the target molecule. An example is demonstrated with MD simulation applied to the ionic liquid molecule N-methyl-N-propylpiperidinium bis trifluoromethanesulfonyl imide (PP13-TFSI). The origin and stability of HOMO–LUMO gap are discussed.