#!/bin/sh
# Calculation of the excitation energies of beta-Carotene using the TD-DFT+TB
# method. This method is meant for GGA or LDA functionals. In this example PBE
# is used during the SCF. In the the calculation of the excitation energies the
# TD-DFTB+TB method is used in which the required integrals are approximated in
# the same way as in a TD-DFTB calculation. Symmetry NOSYM is required.
# The key MODIFYEXCITATION allows to remove single orbital transitions based on
# certain criteria. For example, for a large calculation, one can combine
# several of the filtering techniques with the key MODIFYEXCITATION. If one uses
# the next input, only the lowest 10000 single orbital transitions are used
# (which have the lowest orbital energy differences). Out of these 10000 the
# single orbital transitions with an oscillator strength smaller than 0.001 are
# removed, and single orbital transitions are removed that have an energy
# difference larger than 1.0 Hartree. In the space of single-orbital transition
# that are left the lowest 1000 eigenvectors are calculated.
# ModifyExcitation
# UseOccVirtNumbers 1 10000
# OscStrength 0.001
# UseOccVirtRange 0.0 1.0
# End
# Excitations
# TDDFTB
# OnlySing
# Lowest 1000
# End
# In the actual example only single orbital transitions with an oscillator
# strength smaller than 0.001 are removed, which one might do if one is
# interested only in excitation energies with a high oscillator strength.
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