Tight-binding modelling with DFTB

Benjamin Hourahine
Department of Physics, University of Strathclyde, John Anderson Building,107 Rottenrow, Glasgow G4 0NG, UK

This lecture and the associated practical laboratory will cover the principles and use of Density Functional based Tight Binding (DFTB). This is an accurate semi-empirical method explicitly derived from Kohn-Sham DFT by making an expansion of the total energy functional around a reference charge density. The zero-th order expansion is similar to standard non-self-consistent tight-binding theory, while the second order leads to transparent parameter-free expressions which include the effects of self-consistent redistribution of Mulliken charges (SCC-DFTB) and spin polarization. DFTB has been successfully applied to many problems where the deficiencies of standard tight-binding become obvious. More information about DFTB is available at http://www.dftb.org

In the last few years the DFTB method has been extended to allow investigation of problems including electronic transport, optical and excited state spectroscopies, hydrogen-bonded, complex magnetic and strongly correlated materials. DFTB also can be used with a range of linear scaling approaches for the simulation of large systems. Applications of DFTB in several areas of materials science will be reviewed in the invited ACCMS-5 conference talk of Dr. Aradi and Prof. Frauenheim.

The practical session will give you experience in running the new DFTB+ code, which is available free for academic use as well as a commercial module for the Accelyris materials studio system. DFTB+ can model periodic, embedded and cluster/molecular systems efficiently. Example systems relevant to several of the themes from the main conference will be used to illustrate properties which can be calculated with DFTB+.