The programs LMTRANS and LMFIT can be used to construct quasi-diabatic dipole and polarisability surfaces within the VCHAM framework.

The LMTRANS program is first used to read the output of quantum chemistry calculations of the adiabatic dipole matrix. The dipole matrix is then transformed to the diabatic representation using the eigenvectors of a given VCHAM potential, determined from the model potential read from a .VCHAM file created using VCHFIT. The same can also be achieved for the polarisability tensor. The resulting diabatic dipole matrix (and/or polarisability tensor) is then written to a database for use in a fitting procedure.

The LMFIT program is then used to fit a simple fourth-order Taylor expansion to the elements of the diabatic dipole matrix and polarisability tensor written to the database file. Elementary group theoretical arguments are used to determine which terms of the expansions are necessarily zero. The fitting is performed in terms of the ground state mass- and frequency-scaled normal modes used by the VCHAM programs.

The LMPLOT program is used to visualise the output of the LMTRANS and LMFIT programs.