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Sextic force fields

Internal coordinate quartic force fields have been computed for relatively large systems, e.g., for the 17-atom amino acid L-proline [70]. Nevertheless, despite the fact that electronic-structure programs to compute analytic geometric first and second derivatives of the energy have become available at almost any level [71-74], to the best of our knowledge [68], complete sextic force fields in internal coordinates are available only for a handful of triatomic systems, N2O [75-78], CO2 [79-82], and H2O [48,59]. This is due to several factors. First, it is exceedingly difficult to determine accurate higher-order force constants strictly from experimental information. Second, force fields computed from most electronic-structure... [Pg.162]

Kobayashi, M., Suzuki, I. Sextic force-field of nitrous-oxide, J. Mol. Spectry. 1987,125, 24M2. [Pg.173]

Values reported for r(N=N) and r(N=0) correspond to the minimum of residuals achieved from a global fit of the equilibrium stmctuie and sextic force field to a set of molecular band constants, belonging to six isotopomers. [Pg.343]

Species for which full sextic force fields have been determined are printed in bold face (CO2, H2O, and N2O). [Pg.14]

Table 5 suggests that one might hope to determine all the constants in the most general anharmonic force field without too much difficulty. The comparison of Suzuki s with Chedin and Cihla s results in Table 6 gives some feel for the reliability of the results obtained. These two calculations were made in different ways (see the original references) although both refined the force field to fit all observed vibrational levels and rotational constants, Suzuki used an up-to-quartic force field, where Chedin and Cihla used an up-to-sextic force... [Pg.145]

VBOs applying Chedin s sextic empirical force field [80] are presented in Table 9.3 for 02 using exactly the same potential with the internal and normal coordinate Hamiltonians. When comparison can be made, the two approaches result in the same eigenenergies. It is also worth mentioning that for CO2 no convergence (singularity) problems appeared, in clear contrast to the case of fhe nonlinear H2O molecule. [Pg.168]

Sextic centrifugal CaPySai In addition cubic force field... [Pg.276]


See other pages where Sextic force fields is mentioned: [Pg.21]    [Pg.322]    [Pg.20]    [Pg.21]    [Pg.322]    [Pg.20]    [Pg.21]    [Pg.21]    [Pg.275]    [Pg.140]    [Pg.29]   
See also in sourсe #XX -- [ Pg.3 , Pg.162 ]

See also in sourсe #XX -- [ Pg.162 ]

See also in sourсe #XX -- [ Pg.162 ]




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