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Calculation of vibrational frequencies through a variational reduced-coupling approach
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10.1063/1.2798104
/content/aip/journal/jcp/127/16/10.1063/1.2798104
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/16/10.1063/1.2798104

Figures

Image of FIG. 1.
FIG. 1.

Histogram representation of the absolute value of the off-diagonal element of the standard VCI matrix and the STA-VCI matrix for methanol using the same basis. For the STA-VCI method, the OH-stretch mode is coupled to all other modes . Note the difference in the occurrence of off-diagonal elements between standard VCI and STA-VCI.

Tables

Generic image for table
Table I.

Representative timing for the construction of the potential energy surface (PES) and the Hamiltonian VCI matrix for aliphatic alcohols for both standard VCI (full) and STA-VCI (STA) methods. All timings are relative to methanol using the standard VCI method. We also report the observed computational scaling determined by a linear regression of ln(time) vs , where is the number of normal modes.

Generic image for table
Table II.

Convergence of the fundamental OH-stretch vibrational frequency as a function of , computed with both standard VCI and STA-VCI methods for an MP2/SBK(d,p) PES. The VCI basis-set size is indicated by . All frequencies are given in .

Generic image for table
Table III.

Fundamental OH-stretch vibrational frequency computed with standard VCI and STA-VCI methods for an MP2/SBK(d,p) PES. The VCI basis includes either single and double excitations (SD); single, double, and triple excitations (SDT); or single, double, triple, and quadruple excitations (SDTQ). The resulting VCI basis size is indicated by . All frequencies are given in .

Generic image for table
Table IV.

Fundamental OH-stretch vibrational frequency computed with VCI (full), STA-VCI (STA), CC-VSCF (full), and STA-CC-VSCF (STA) methods for different levels of ab initio theory. Deviation from the experimental value (Ref. 35) is given in parentheses.

Generic image for table
Table V.

Fundamental OH-stretch frequency for benzoic acid, computed with STA-VCI using increasingly larger VCI basis sets and CC-VSCF and using an MP2/SBK(d,p) PES. Difference from the estimated experimental value is given in the row . All frequencies are given in .

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/content/aip/journal/jcp/127/16/10.1063/1.2798104
2007-10-31
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Calculation of vibrational frequencies through a variational reduced-coupling approach
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/16/10.1063/1.2798104
10.1063/1.2798104
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