TOMBO: All-electron mixed-basis approach to condensed matter physics

TOMBO is a computer code for calculating the electronic structure of systems that consist both of core and valence electrons and nuclei, based on density-functional theory. It is based on an all-electron mixed-basis approach, in which the Kohn-Sham (KS) wave function is expressed by a linear combination of plane-waves and atomic-orbitals. This approach can describe both spatially localized and extended orbitals, which enables us to perform all-electron calculations with high accuracy from isolated clusters to periodic crystals. The present paper describes a theory of the all-electron mixed-basis approach, as well as input variables and benchmark tests in TOMBO. The algorithm for accelerating the computational time that is needed to solve the KS equation is also presented. (C) 2014 Elsevier B.V. All rights reserved.