## 52.3 Special options for Intensities

INTENSITY,options

The INTENSITY directive of the SURF program provides the option to alter the electronic structure methods for calculating the dipole surfaces. It also allows to define the VARDIPnD[X,Y,Z] variables separately. describes the dimension of the coupling surface and can be chosen to be 1 - 4.

Dipole surfaces can be computed for all those methods for which analytical gradients are available in MOLPRO. For all methods except Hartree-Fock this requires the keyword CPHF,1 after the keyword for the electronic structure method. In multi-level schemes for which the variables VAR1D, VAR2D and VAR3D are set individually, the VARDIPnD[X,Y,Z] variables have to be set accordingly. Symmetry is currently only implemented for the 1D, 2D and 3D dipole surfaces. For 4D terms symmetry will automatically switched off at the moment. The determination of dipole surfaces beyond Hartree-Fock quality effectively doubles the computation time for surface calculations.

DIPOLE=n
Allows to switch between the different dipole surface calculations.
DIPOLE=0 switches of all dipole calculations. DIPOLE=1 (this is the default) computes the dipole surfaces at the Hartree Fock level of theory, and therefore does not increase the computation time of electronic structure theory. DIPOLE=2 switches on the dipole surfaces at the full level of theory therefore CPHF,1 is required, this effectively doubles the computation time for surface calculations.
NDIMDIP=n
This denotes the term after which the -body expansion of the dipole surfaces is truncated. The default is set to 3. Note that NDIMDIP has to be lower or equal to NDIM.
VARDIP1DX=variable
Variable which is used for the direction of the dipole moment for 1D surfaces.
VARDIP1DY=variable
Variable which is used for the direction of the dipole moment for 1D surfaces.
VARDIP1DZ=variable
Variable which is used for the direction of the dipole moment for 1D surfaces.
POLAR=n
By default (POLAR=0) Raman intensities will not be computed. POLAR=1 switches the calculation of polarizability tensor surfaces on. Note that currently only Hartree-Fock polarizabilities are supported, which requires the POLARI keyword in the Hartree-Fock program.
NDIMPOL=n
This variable denotes the term after which the -body expansion of the polarizability tensor surfaces is truncated. The default is set to 2. Note that NDIMPOL has to be lower or equal to NDIM and must be smaller than 4.
VARPOL1DXX=variable
Variable which is used for the component of the polarizability tensor for 1D surfaces.
VARPOL1DYY=variable
Variable which is used for the component of the polarizability tensor for 1D surfaces.
VARPOL1DZZ=variable
Variable which is used for the component of the polarizability tensor for 1D surfaces.
VARPOL1DXY=variable
Variable which is used for the component of the polarizability tensor for 1D surfaces.
VARPOL1DXZ=variable
Variable which is used for the component of the polarizability tensor for 1D surfaces.
VARPOL1DYZ=variable
Variable which is used for the component of the polarizability tensor for 1D surfaces.
The higher order terms VARDIPnD[X,Y,Z] and VARPOLnD[XX,,YZ] can be defined the same way. An example for a calculation, which provides both, infrared and Raman intensities, is given below.

label1
{hf
start,atden
polari}

{surf,start1D=label1,ndim=3,info=1
intensity,polar=1,ndimpol=3
scalnm,auto=on }

vscf,polar=1,ndimpol=3,info=1
vci,version=4,polar=1,ndimpol=3,info=1

molpro@molpro.net 2019-06-16