Hypertext Dalton 2.0 manual - Theoretical Chemistry, KTH

Chapter 16
Vibrational corrections
dalton provides an efficient automated procedure for calculating rovibrationally averaged
molecular r α geometries, as well as an automated procedure for calculating vibrational
averages of a large range of second-order molecular properties, for SCF and MCSCF wave
functions. In the current implementation, it is not possible to exploit point-group symmetry,
and one must ensure that the symmetry is turned off in the calculation.
Reference literature:
Effective geometries: P.-O. Åstrand, K. Ruud and P. R. Taylor.
J.Chem.Phys, 112, , 2655 (2000).
Vibrational averaged properties: K. Ruud, P.-O. Åstrand and P. R. Taylor.J.Chem.Phys.,
112, 2668, (2000).
Temperature and isotope effects: K. Ruud, J. Lounila and J. Vaara.
J.Chem.Phys., to be published.
16.1 Effective geometries
The (ro)vibrationally averaged geometries can be calculated from a knowledge of part of
the cubic force field
〈r i 〉 = r e,i − 1
4ω 2 i
3N−6 ∑
j=1
V (3)
ijj
ω j
(16.1)
where the summation runs over all normal modes in the molecule and where ω i is the
harmonic frequency of normal mode i and V (3)
ijj is the cubic force field. A typical input
for determining (ro)vibrationally averaged Hartree–Fock geometries for different water isotopomers
will look like
**DALTON INPUT
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