DTMM and COSMIC molecular mechanics parameters for alkylsilanes

Harmonic DTMM and COSMIC molecular mechanical force fields were extended to cover aliphatic silanes. Structures of the thirty-five molecules were exam ined and they generally fit approximately within experimental error. For th ese, root mean square deviations between the calculated and the experimenta lly determined geometrical data were found to be less than 0.05 Angstrom an d 1.7 deg. for bond lengths and bond angles, respectively. The accuracy of these force fields was also verified in comparison with the other force fie lds (MM2, MM3), semi-empirical (PM3), ab initio (HF, MP2) and density funct ional (B3LYP, BP86) quantum chemical methods. The relative stability of the seventeen conformations of seven simple molecules was investigated and the limitations of the DTMM software is discussed. (C) 1999 Elsevier Science B .V. All rights reserved.