10.1021/jz401181q.s001
Eugene Kamarchik
Eugene
Kamarchik
Ahren W. Jasper
Ahren W.
Jasper
Anharmonic Vibrational Properties from Intrinsic <i>n</i>‑Mode State Densities
American Chemical Society
2015
density
CH
C 3H Truncation
state densities
Anharmonic Vibrational Properties
method
anharmonic vibrational result
energy surface
mode pairing
partition functions
anharmonic vibrational state counts
modes yields
quantity
2015-12-16 23:15:09
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Anharmonic_Vibrational_Properties_from_Intrinsic_i_n_i_Mode_State_Densities/2024784
A method for calculating fully anharmonic
vibrational state counts,
state densities, and partition functions for molecules is presented.
The method makes use of a new quantity, the <i>intrinsic</i> density of states, which is associated with the states that uniquely
arise from a given mode, mode pairing, or higher-order mode coupling.
By using only low-order intrinsic densities, the fully coupled anharmonic
vibrational result can be constructed, as shown by our application
of the method to methane, CH<sub>4</sub>, and cyclopropene, C<sub>3</sub>H<sub>4</sub>. Truncation of the intrinsic expansion at the
coupling of pairs of modes yields greatly improved scaling over direct
evaluation of the full-dimensional result and recovers a large fraction
of the total anharmonicity. We also discuss the relation of the new
quantities to the structure of the potential energy surface.