The extended Bloch functions are used frequently for description of crystal electronic behavior in reciprocal space. However this extended representation is not appropriate for calculation of properties related to electron behavior in real space such as Electron Traort and localization of electron in nano structures. An alternative approach for description of electronic behavior in real space is use of a set of localized functions such as maximally localized Wannier functions for representation of crystal orbitals. Wannier90 is an efficient package for calculation of maximally localized Wannier functions from the data of any computational ab-initio package. In this thesis, I have developed an interface program for converting the output eigenfunctions and eigenvalues of Wien2k code to the required input matrices for the Wannier90 code, to generate the maximally localized Wannier functions from the outputs of Wien2k that is a full potential electron wave functions package. The main inputs for Wannier90 code are wave functions overlap matrix elements and first-guess Wannier functions. In Wien2k, the basis functions and the overlap matrix elements are divided in to two parts, inside the atomic sphere and in the interstitial region. In this project, first we applied appropriate changes to extract wave function from the Wien2k calculations and then implemented proper programs for calculating the overlap matrix elements inside the atomic sphere and interstitial region. This software is able to calculate first-guess matrix for 36 hybrid orbital, Moreover first-guess Wannier function can be both atom center and bond center. Finally with this interface software of Wien2k and Wannier90, the Wannier function for bulk of Carbon and Silicon are calculated and verified by comparing the resulting band structure with the reliable first principle band structures. The developed software in this thesis is named Isfahan2.9. Key Words : MLWF'S, Bloch functions, Wien2k, Wannier90, Interface, Muffin-Tin, Lapw.
