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.
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.
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 .
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 .
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.
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 .
Article metrics loading...
Full text loading...