Example: sTDA excitation energies wB97: TCNE-Benzene¶

#! /bin/sh


# Calculation of the excitation energies of the complex TCNE-Benzene using the
# simplified Tamm-Dancoff (sTDA) method by Grimme, for a range-separated
# function. This method is meant for hybrid functionals or range-separated
# functionals during the SCF. In this example the range-separated functional 
# wB97 is used during the SCF. In the the calculation of the excitation
# energies the sTDA method is used in which the required integrals are
# approximated. For range-separated functional one needs to set the parameters
# manually. Note that the alpha and beta parameters for sTDA for range separated
# functionals in the Risthaus paper (dx.doi.org/10.1039/C3CP54517B) are mixed
# up. A TZP or TZ2P basis set is recommended for this method.

# For the excitation energies of the complex TCNE-Benzene, charge 
# transfer (CT) states are important. Symmetry NOSYM is required.
# The subkey DESCRIPTORS is added to the key EXCITATIONS such that CT descriptors 
# are calculated. The the atomic distance criterion used for the calculation of 
# CT_AT was set to 3.0 Angstrom.
# The sTDA parameters should be set with the subkeys GRIMMEAEX, GRIMMEALPHA, and
# GRIMMEBETA of the key MODIFYEXCITATION.

$AMSBIN/ams <<eor
System
  atoms
     C     -2.274205   -1.398789   -0.000000
     C     -2.274206    1.398791   -0.000000
     C     -2.274506   -0.699551    1.213150
     C     -2.274505   -0.699551   -1.213150
     C     -2.274506    0.699551    1.213150
     C     -2.274505    0.699551   -1.213150
     H     -2.278385   -2.491323   -0.000000
     H     -2.278386    2.491321   -0.000000
     C      1.368996   -0.686302    0.000000
     C      1.368996    0.686301    0.000000
     C      1.379968   -1.434052   -1.220900
     C      1.379968   -1.434052    1.220895
     C      1.379968    1.434051   -1.220900
     C      1.379967    1.434051    1.220895
     N      1.400955   -2.054479   -2.204820
     N      1.400955   -2.054479    2.204824
     N      1.400955    2.054481   -2.204820
     N      1.400954    2.054481    2.204824
     H     -2.276046   -1.246672    2.158733
     H     -2.276045   -1.246672   -2.158730
     H     -2.276045    1.246671   -2.158730
     H     -2.276046    1.246671    2.158733
  end
end

Task SinglePoint

Engine ADF
  excitations
    descriptors
    descriptors_ct_at_rab 3.0
    onlysing
    stda
  end
  Basis
    Type DZ
    Core None
    CreateOutput yes
  End
  modifyexcitation
    grimmeaex 0.61
    grimmealpha 4.41
    grimmebeta 8.00
    grimmepertc
  end
  symmetry nosym
  xc
    libxc wB97
  end
EndEngine

eor