[gmx-users] keep atoms planar

[Rongliang Wu]

hello, 

i found in ffoplsaa.itp :

[ dihedraltypes ]
; Improper OPLS dihedrals to keep groups planar.
; (OPLS doesnt use impropers for chiral atoms).
; Since these functions are periodic of the form 1-cos(2*x), the are actually
; implemented as proper dihedrals [1+cos(2*x+180)] for the moment, 
; to keep things compatible.
; The defines are used in ffoplsaa.rtp or directly in your .top ile.

; O?-C -X -Y improper torsion. C can be C_2 or C_3 too.
#define improper_O_C_X_Y        180.0     43.93200   2

; X-NO-ON-NO improper torsion.
#define improper_X_NO_ON_NO     180.0     43.93200   2

; N2-X-N2-N2 improper torsion.
#define improper_N2_X_N2_N2     180.0     43.93200   2

; Z -N?-X -Y improper torsion
#define improper_Z_N_X_Y        180.0      4.18400   2

; Z -CM-X -Y improper torsion. CM can be C= too.
#define improper_Z_CM_X_Y       180.0     62.76000   2

; Z -CA-X -Y improper torsion. CA is any ring carbon (CA,CB,CN,CV,CW,CR,CK,CQ,CS,C*)
#define improper_Z_CA_X_Y       180.0      4.60240   2
 				

are X Y Z designate any atom types? 
--------------
Rongliang Wu
2006-03-14