TOMBO Ver.2 Manual

Chapter 3
Input Files
To perform a LDA or GW calculation of an isolated system (atoms, molecules, or clusters),
TOMBO needs two input files, COORDINATES.inp and INPUT.inp. These are the
central input files of TOMBO. The variables related to the unit cell, atomic positions, and
also AOs are written in COORDINATES.inp: the lattice constant, lattice vectors, coordinates
of the nuclei and the number of orbital-types of AOs for each atom. On the other
hand, INPUT.inp determines "what to do and how to do it", and can contain a relatively
large number of parameters. In a crystal calculation within a LDA level, two other input
files, SPOINT.inp and KPOINT.inp, are required to assign special k points to do specialpoint
sampling within the irreducible wedge of the 1st Brillouin zone (BZ) during the selfconsistent
field (SCF) loop and output k points to draw band structure diagram, respectively.
Usually, the special points are given on the Monkhorst–Pack grid in the irreducible BZ. For
a GW crystal calculation, the assignment of KPOINT.inp is different from a LDA calculation,
and another input file QPOINT.inp is also required In order to calculate the polarization
function P GG ′ for each momentum transfer q (and for each energy transfer ω in the case of
the full ω integration), k-point sampling is performed for the points on the Gamma grid
in the whole BZ assigned as “sum” in KPOINT.inp. Then the correlation part of the selfenergy,
Σ c is calculated by taking q-point summation on the Γ-grid in the irreducible BZ by
using QPOINT.inp. Finally, the quasiparticle energies as well as the expectation values of
the LDA exchange-correlation potential, and the exchange (Σ x ) and correlation (Σ c ) parts of
the self-energy are evaluated for the k points (typically at symmetry points in the irreducible
BZ) assigned as “out” in KPOINT.inp.