I have done anharmonic frequency calculations in Gaussian09.(for acetone). At the end of the output file I can see the anharmonic frequencies. I do not see anharmonicity constant value(for different vibrational modes) though. Can we get anharmonicity constant value?
Also, I want to know how are anharmonic frequencies calculated? What theory is encoded within Gaussian software to calculate these values? How reliable are those?
Any reference paper will help.
Thank you.
For the constants I can't help you further, but concerning the calculation you can find the references at:
http://sobereva.com/g09/k_freq.htm
" Numerical differentiation can also be performed along modes to compute zero-point energies, anharmonic frequencies [Califano76, Miller80, Papousek82, Clabo88, Page88, Miller90, Page90, Barone04, Barone05], and [...]"
Jürgen Weippert I have looked into the link. It does not have details about the calculations, rather just a one line description, which is not really helpful for me. Do you know any reference paper that gauusian has used to encode the anharmonic frequencies.
Thank you.
The reference papers are supposed to be in the links [Califano76, Miller80, Papousek82, Clabo88, Page88, Miller90, Page90, Barone04, Barone05]. Did you go through all of them? At first glance at least Barone05 is definitely about anharmonicity.
More complex problem is non-linearity. It is not solved.
Not any non-linear problem can be solved by linear approximations.
Jürgen Weippert I was not aware that they were reference link. Thanks. I will sure look into them.
From that list, I recommend
[Clabo et al., Chem. Phys. 123, 187 (1988)]
for a general idea of the VPT2 theory and
[V. Barone, J. Chem. Phys. 120, 3059 (2004)]
[V. Barone, J. Chem. Phys. 122, 014108 (2005)]
[Bloino et al., J. Chem. Theory Comput. 8, 1015 (2012)]
for the implementation in Gaussian. The last reference is the version implemented in Gaussian 16
- Badges
- Science topic