The consistent force field (CFF) has been designed for the calculation of structures, energies, and vibrational frequencies of both small organic molecules and large biomolecular systems, induding peptides, proteins, nudeic acids, carbohydrates, and lipids, in vacuo and in the condensed phase [66]. It differs from empirical force fields in that its force constants are derived from a generalizable quantum mechanical procedme. The authors call this a quantum mechanical force field (QMFF), because observables generated ab initio describe the energy hypersurface of a family of molecules [67]. Scaling of the QMFF force constants gives the final values for CFF, because it is well known that force constants derived from Hartree-Fock theory tend to be too large, and bond lengths tend systematically to be too smah.  [c.354]

Each nonzero element in the butadienyl input is 1. The input element 1.0 also works but locations, for example, the 1,2 location, must be specified by integers. In some applications, for example, pyridine (Chapter 7). decimal inputs other than 1,0 are used. Substitute 1.PRINT for PRINT in QMOB.AS to obtain hard copy. Draw diagrams analogous to Fig, 6-3 that show the energy levels in their proper order, lowest to highest. If an energy turns out to be zero (relative to a), label it uouboudiug, /(, Remember that, because of rounding and a finite number of matrix rotations, that the zero roots may be output as very small values, say 10 or so.  [c.196]

For the unfired example. Fig. 9.2a, the efficiency is 0.25, and EUF = (W -t- QuMF = (1 -t- 2.25)/4 = 0.8125. For the supplementary fired example of Fig. 9.2b, the efficiency remains at 0.25 but the EUF becomes  [c.168]

See pages that mention the term QMOBAS : [c.360]    [c.196]    [c.54]    [c.198]    [c.230]    [c.449]    [c.90]    [c.54]    [c.25]   
Computational chemistry using the PC (2003) -- [ c.194 ]