1.1 Introduction

BAND is a program for calculations on periodic systems, i.e. polymers, slabs and crystals, and is supplemental to the molecular ADF program for non-periodic systems. It employs density functional theory in the Kohn-Sham approach. BAND is very similar to ADF in the chosen algorithms, although important differences remain. Like ADF, BAND makes use of atomic orbitals, it can handle elements throughout the periodic table, and has several analysis options available. Unlike ADF, BAND can use numerical atomic orbitals, so that the core is described very accurately. Because of the numerical orbitals BAND can calculate accurate total energies. Furthermore it can handle basis functions for arbitrary l values.