Hypertext Dalton 2.0 manual - Theoretical Chemistry, KTH

CHAPTER 11. CALCULATION OF OPTICAL AND RAMAN PROPERTIES 95
11.4 Vibrational Raman Optical Activity (VROA)
Reference literature:
MCSCF: T.Helgaker, K.Ruud, K.L.Bak, P.Jørgensen, and J.Olsen.
Faraday Discuss., 99, 165, (1994).
DFT: K.Ruud, T.Helgaker, and P.Bour. J. Phys. Chem. A, 106, 7448,
(2002).
The calculation of vibrational Raman intensities and vibrational Raman optical
activity (VROA) is one of the more computationally expensive properties that can be evaluated
with dalton.
Due to the time spent in the numerical differentiation, we have chosen to calculate
ROA both with and without London atomic orbitals in the same calculation, because the
time used in the set-up of the right-hand sides differentiated with respect to the external
magnetic field is negligible compared to the time used in the solution of the time-dependent
response equations [42]. Because of this, all relevant Raman properties (intensities and
depolarization ratios) is also calculated at the same time as ROA.
A very central part in the evaluation of Raman Optical Activity is the evaluation
the electric dipole-electric dipole, the electric dipole-magnetic dipole, and the electric
dipole-electric quadrupole polarizabilities, and we refer to Section 9.4 for a more detailed
description of the input for such calculations.
When calculating Raman intensities and ROA we need to do a numerical differentiation
of the electric dipole-electric dipole, the electric dipole-magnetic dipole, and the electric
dipole-electric quadrupole polarizabilities along the normal modes of the molecule. The procedure
is described in Ref. [42]. We thus need to do a geometry walk of the type numerical
differentiation. In each geometry we need to evaluate the electric dipole-electric dipole, the
electric dipole-magnetic dipole, and the electric dipole-electric quadrupole polarizabilities.
This may be achieved by the following input:
**DALTON INPUT
.WALK
*WALK
.NUMERI
**WAVE FUNCTIONS
.HF
*HF INPUT
.THRESH
1.0D-8
**START