## Abstract MMVB is a QM/MM hybrid method, consisting of a molecular mechanics force field coupled to a valence bond Heisenberg Hamiltonian parametrized from __ab initio__ CASSCF calculations on several prototype molecules. The Heisenberg Hamiltonian matrix elements __Q__~__ij__~ and __K__~__ij__~,
Application of a simple diagonal force field to the simulation of cyclopentane conformational dynamics
β Scribed by Cornell, Wendy D.; Ha, Maria P.; Sun, Yax; Kollman, Peter A.
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 666 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0192-8651
No coin nor oath required. For personal study only.
β¦ Synopsis
Molecular dynamics simulations have been carried out on the cyclopentane molecule using a diagonal force field and the results compared with both experiment and a recent study which used the MM3 force field [W. Cui, F. Li, and N. L. Allinger, I. Am. Chem. Sac., 115,2943 (199311. The current simulation resulted in an RMS pseudorotational velocity of 1036 deg/ps, compared to the model estimated value of 400 deg/ps and the MM3 result o,f 1700 deg/ps. The pseudorotation amplitude w,as calculated to be 0.46 0.02 A, coGpared to the experimental value of 0.48 A and the MM3 value of 0.5 f 0.03 A. The two distinct average C-H bond lengths seen for the axial and equatorial conformations in the MM3 simulation were not observed. The energy barrier to passing through the planar conformation was calculated at 4.7 kcal/mol as compared to the experimental value of 5.2 kcal/mol and the MM3 value of 4.2 kcal/mol. During the simulation, the angle bending term dominated the potential energy, followed by the torsion energy, as was seen with MM3. The third largest energy term was the bond stretching, followed by the van der Waals interaction, the reverse of what was seen with MM3. The effects of carrying out the simulation under conditions of constant energy versus constant temperature are discussed.
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