Tight-binding studies of bulk properties and hydrogen vacancies in KBH4

We present computational studies of the bulk properties and hydrogen vacancies in KBH4 using tight-binding (TB) calculations. The NRL-TB method was used to construct a TB Hamiltonian by fitting the density-functional theory (DFT) data for the electronic energies for the tetragonal and cubic phases of KBH4 as a function of volume. Our approach allows for computationally efficient calculations of phonon frequencies and elastic constants, mean-square displacements, and formation energies of hydrogen vacancies using the static and molecular dynamics modules of the NRL-TB code. We find that the results for the bulk properties and hydrogen vacancies given by TB calculations are comparable to those given by DFT calculations.