7336
J . Am. Chem. Soc. 1984, 106, 7336-7347
p ( r ) is taken as function of the coordinates to permit a fast evaluation of it and of its first and second derivatives. V,(r) includes contributions from bonding, bond angle, torsion angle, and nonbond interaction terms and is introduced as an analytical function of the coordinates, V,(r) = f/zXDb[exp(-2a(b - bo)) - 2 exp(-a(b
- bo))] +
+ ‘/,CKx(Xi- x,)’ + X Ci F ( q i - q,)2 + I
Y2cK,(l)
COS
1
j/2cKaw(Oi- Oo)(O’i i
di + y 2 c K + ( 2cos ) 2di + i
- e), cos d i + C [ A exp(-pru) - Brijd] ij
where bi are bond distances, Oi are bond angles, di are torsion angles, qi are 1-3 nonbonded distances, rij are all higher order nonbond distances, and x are out of plane angles. D, a, b, KO, Bo, F, q, Kx, K+, K,., KO@,A, B, and p are adjustable parameters which depend on the type of atoms involved. The *-potential term, corrected for nearest-neighbor orbital overlap is V*O(r) = CP,,(r) [ h ~ , ( r ) ~ , , ( r ) h ~ , , ( r )+ ?4p,,(r)A7,p(~)1 a
2 c P,A~)AP,v(r)P
