+ double Smixed; /* mixed S radius */
+ double Rmixed; /* mixed R radius */
+ double A[2]; /* factor of tersoff attractive part */
+ double B[2]; /* factor of tersoff repulsive part */
+ double Amixed; /* mixed A factor */
+ double Bmixed; /* mixed B factor */
+ double lambda[2]; /* tersoff lambda */
+ double lambda_m; /* mixed lambda */
+ double mu[2]; /* tersoff mu */
+ double mu_m; /* mixed mu */
+
+ double chi;
+
+ double beta[2];
+ double n[2];
+ double c[2];
+ double d[2];
+ double h[2];
+
+ t_tersoff_exchange exchange; /* exchange between 2bp and 3bp calc */