Factors Contributing to the Accuracy of Harmonic Force Field Calculations for Water

Table 6. Comparison of contributing factors of uncertainty. RSS represents the square root of the sum of the squares of each contributing factor. |error| represents the average absolute difference between the experimental³⁴ and computed harmonic vibrational frequencies. All units are cm^-1.

FIGURE CAPTIONS

Figure 1. Average difference (||) between computed vibrational frequencies with increasing basis set size. Computations were performed at the varying levels of theory and increasing basis set size.
Figure 2. Average difference (|error|) between experimental harmonic frequencies and vibrational frequencies computed with the cc-pVTZ basis set and increasing levels of theory.
Figure 3. Average difference (||) between vibrational frequencies computed with the cc-pVTZ basis set and increasing levels of theory.
Figure 4. Average difference (|error|) between experimental harmonic frequencies and vibrational frequencies computed with the CCSD(T) method and increasing basis set size. All electrons were included in post-SCF calculations in the CCSD(T) core computation. Core electrons were frozen in the other computations.
Figure 5. Average difference (|error|) between experimental harmonic frequencies and relativistically corrected vibrational frequencies computed at the CCSD(T) level of theory with increasing basis set size. CG computations were performed using the Cowan-Griffin method. DK computations were performed using the Douglas-Kroll method.

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