The LMTRANS program is first used to transform the calculated
adiabatic dipole matrix to the (quasi) diabatic representation. To do
so, the input file nh3_d3h_q1_dip.inp is
used. The normal modes are read from the Gaussian output file
nh3_d3h_freq.log, and
the names of Molpro output files containing the adiabatic dipole matrix
calculated at the EOM-CCSD/aug-cc-pVDZ level at points along the
invedrsion coordinate Q1 are specified in the
file q1_dip.set. Notice
the use of the negphase
keyword to flag when a change in
phase causes the transition dipole moments between states 1 and 2 to
change sign. The rotation of the dipole matrix to the (quasi) diabatic
representation is achieved using the eigenvectors of a vibronic coupling
Hamiltonian written to the
file nh3_d3h_q1_fit.vcham using
the VCHFIT program. Running the lmtrans program using
the command
lmtrans nh3_d3h_q1_dip.inp
results in the creation of the database file nh3_d3h_q1_dip.dat. This file contains for each file specified in the file q1_dip.set nuclear geometry in both Cartesian coordinates and normal modes, and the dipole matrix in both the adiabatic and (quasi) diabatic representations. This database can now be used in a subsequent fitting procedure using the LMFIT program.
Using the database file nh3_d3h_q1_dip.dat, fits to the elements of the (quasi) diabatic dipole matrix along the mode inversion mode Q1 are made using the LMFIT program. The input file nh3_d3h_q1_lmfit.inp is used. The LMFIT program can only handle Abelian point groups. Hence, the highest subgroup of the D3 point group of the reference geometry is used, that is, the C2v point group. Note that attention has to be paid to ensuring that the state and axis symmetries are correct for the orientation of the molecule at the reference geometry. Running the lmfit program using the command
lmfit nh3_d3h_q1_lmfit.inp
results in the creation of the file nh3_d3h_q1_lmfit.lmi, which contains the values of the fitted parameters of the Taylor expansions of the (quasi) diabatic dipole matrix elements.
Using the LMPLOT program, the model dipole matrix elements contained in the file nh3_d3h_q1_lmfit.lmi and/or the calculated dipole matrix elements contained in the database file nh3_d3h_q1_dip.dat may be visualised. For example, to plot the z-component of the (quasi) diabatic transition dipole moment between the states 1 and 2 along the mode Q1, the following command woud be used:
lmplot -dipole z 1 2 nh3_d3h_q1_lmfit 1