44.1 Options

The following options are available:

PMP=value

Vibrational angular momentum terms (Coriolis coupling), i.e. $\frac{1}{2} \sum_{\alpha\beta} \hat{\pi}_\alpha\mu_{\alpha\beta} \hat{\pi}_\beta$, and the Watson correction term are by default switched off. PMP=1 adds the Watson correction term (see eq. 20) as a pseudo-potential like contribution to the fine grid of the potential. PMP=2 allows for the calculation of the integrals of the PMP operator using the approximation that the $\mu$ tensor is given as the inverse of the moment of inertia tensor at equilibrium geometry.

COMBI=value

By default the VSCF program calculates the fundamental modes of the molecule only. However, choosing COMBI=1 allows for the calculation of the first vibrational overtones and $n\times(n-1)/2$ combination bands consisting of two modes in the first vibrational level.

SOLVER=value

For solving the one-dimensional Schrödinger equation two different algorithms can be used. The default, i.e. SOLVER=1, calls the discrete variable representation (DVR) as proposed by Hamilton and Light. Alternatively, the collocation algorithm of Young and Peet can be used (SOLVER=2).

THERMO=value

THERMO=1 allows for the improved calculation of thermodynamical quantities (compare the THERMO keyword in combination with a harmonic frequency calculation). However, the approach used here is an approximation: While the harmonic approximation ist still retained in the equation for the partition functions, the actual values of the frequencies entering into these functions are the anharmonic values derived from the VSCF calculation.

ROTJ=value

Rovibrational levels can be computed in an approximative fashion only (this does not work in combination with the COMBI option). Once the VSCF equations have been solved, the rotational constants will be computed from the vibrationally averaged structures for each vibrational level. This allows for a rough estimate and very fast calculation of the rovibrational levels. ROTJ=$n$ determines the value of $J$. A negative number for $J$ results in a calculation of all rovibrational levels from $J=1$ up to the specified $J$ value.

DIPOLE=value

DIPOLE=1 allows for the calculation of infrared intensities. Calculation of infrared intensities requires the calculation of dipole surfaces within the SURF program. By default intensities will not be computed.

NDIM=value

The expansion of the potential in the VSCF calculation can differ from the expansion in the SURF calculation. However, only values less or equal to the one used in the surface calculation can be used.

INFO=value

INFO=1 provides a list of the values of all relevant program parameters (options).