First-principles electronic structure calculations have been very useful in understanding some of the properties of the new iron-based superconductors. Further explorations of the role of the individual atomic orbitals in explaining various aspects of research in these materials, including experimental work, would benefit from the availability of a tight-binding(TB) Hamiltonian that reproduces ...

A semiempirical approach for calculating the bulk and surface stress is developed and presented in this work. It is based on the tight-binding method with Chadi’s total energy model. A strained system is treated as a perturbation of an unstrained system; the corresponding stress can be calculated by the resolvent Green function method. This approach is applied to an arsenic terminated Si(001)23...

We develop a method and a computer code for the systematic optimization of a transferable tight-binding model for carbon-hydrogen compounds. We take as reference a density-functional theory calculation in the local density approximation and, using a «downhill simplex» routine, we minimize the squared difference between the energies predicted by the reference model and those obtained with our ti...

Wave functions obtained from plane-wave density-functional theory (DFT) calculations using normconserving pseudopotential, ultrasoft pseudopotential, or projector augmented-wave method are efficiently and robustly transformed into a set of spatially localized nonorthogonal quasiatomic orbitals (QOs) with pseudoangular momentum quantum numbers. We demonstrate that these minimal-basis orbitals ca...

Iterative methods such as Lanczos and Jacobi-Davidson are typically used to compute a small number of eigenvalues and eigenvectors of a sparse matrix. However, these methods are not effective in certain large-scale applications, for example, “global tight binding molecular dynamics.” Such applications require all the eigenvectors of a large sparse matrix; the eigenvectors can be computed a few ...

We study the mobility edges in a variety of one-dimensional tight binding models with slowly varying quasi-periodic disorders. It is found that disordered can be approximated by an ensemble periodic models. The determined overlaps energy bands these demonstrate this method provides efficient way to find out precise location edge qusi-periodic Based on approximate method, we also propose index i...