fixed sign

[physik/posic.git] / potentials / tersoff_orig.c

diff --git a/potentials/tersoff_orig.c b/potentials/tersoff_orig.c
index 90121f26bb1cda4855e75abb27a418c66089a177..69b67ace63e630a7a0b6fe623aae269e57094f17 100644 (file)
--- a/potentials/tersoff_orig.c
+++ b/potentials/tersoff_orig.c
@@ -310,7 +310,7 @@ int tersoff_mult_post_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
        else {
                tmp=betaini*pow(zeta,ni-1.0);           /* beta^n * zeta^n-1 */
                b=(1+zeta*tmp);                         /* 1 + beta^n zeta^n */
-               db=chi*pow(b,-1.0/(2*ni)-1);            /* x(...)^(-1/2n - 1) */
+               db=chi*pow(b,-1.0/(2.0*ni)-1);          /* x(...)^(-1/2n - 1) */
                b=db*b;                                 /* b_ij */
                db*=-0.5*tmp;                           /* db_ij */
                v3_scale(&force,&(exchange->dzeta_ij),f_a*db);