# Example: Electric Field, Point Charge(s): N2 and PtCO¶

Download Efield.PntQ_N2.run

#! /bin/sh

# Two illustrations of applying the very useful BASIS keyword and of application
# of an Electric Field.

# For N2, three calculations are provided: 1) a normal N2 run as a reference
# with the BASIS keyword, 2) with a homogeneous electric field, 3) with a point
# charge.

# In this example, no Create run is needed in the input file, because the first
# molecular calculation uses the BASIS keyword. If the $ADFBIN/adf script finds # this keyword, it will first generate a new input file which will then be # executed. The new input file will contain the required Create run for the N # atom in this case. The proper xc functional and relativistic options will # automatically be selected by the BASIS keyword. This includes Dirac # calculations in case of relativistic runs. The output files is identical to # what would have appeared if one would provide the Create runs explicitly in # the input file. It also copies the atomic input, so that everything can be # checked.$ADFBIN/adf -n1 <<eor
title N2  reference for comparison with E-Field runs

atoms
N  0 0 -.55
N  0 0 +.55
end

Basis
Type DZP
Core Small
End

eor

mv TAPE21 N2.t21
rm logfile

$ADFBIN/adf <<eor title N2 in a homogeneous electric field scf converge 1e-8 end atoms N 0 0 -.55 N 0 0 +.55 end fragments N t21.N end EField 0 0 0.01 eor mv TAPE21 N2_field1.t21 rm logfile$ADFBIN/adf <<eor
title  N2 polarized by a point charge on the axis

PointCharges
0 0 3.0 1.0
end

atoms
N 0 0 -.55
N 0 0 .55
end

Fragments
N  t21.N
end

eor

mv TAPE21 N2_field2.t21

# In the second n2 run the homogeneous field is supplied with the key efield,
# used as simple key: one record, data on the same line as the keyword. The
# field strength is specified in atomic units.

# Homogeneous electric fields can be used to study the polarizability: for
# sufficiently small fields the dipole moment should respond linearly.

# For point charges, the third calculation, the block form of the key efield
# must be used. The program first tries to find data on the same line as the
# keyword (defining a homogeneous field). If this is absent, a data block is
# expected with point-charge specifications: x, y, z and q.

# The coordinates are in the same units as in the atoms block (angstrom by
# default) (but always Cartesian). Q is the charge in elementary units (+1 for a
# proton).

# Point charges can be used for instance to simulate crystal fields (Madelung
# potential).

# Note: the symmetry will be determined automatically by the program as C(lin),
# rather than D(lin), in the two runs that involve an electric field: the fields
# break the symmetry.

# For PtCO, a fairly large electric field is applied in combination with a tight
# SCF convergence criterion.

# The BASIS keyword in this example illustrates how different choices can be
# made for different atoms (in this case a frozen core for Pt):
#   Basis
#    Type DZ
#    Core None
#    Pt Pt.4d
#   END


Download Field_PtCO.run

#! /bin/sh

TITLE Pt-CO in electric field

ATOMS
Pt 0 0 0
C  0 0 1.70
O  0 0 2.85
END

Basis
Type DZ
Core None
Pt Pt.4d
End

EFIELD 0 0 0.01

SCF
CONVERGE 1.0E-10
END

BeckeGrid
Quality good
End

eor

mv TAPE21 PtCO.t21