+ /* virial sum and mean virial */
+ moldyn->virial_sum+=v;
+ moldyn->mean_v=moldyn->virial_sum/moldyn->total_steps;
+
+ /* assume up to date kinetic energy */
+ moldyn->p=2.0*moldyn->ekin+moldyn->mean_v;
+ moldyn->p/=(3.0*moldyn->volume);
+ moldyn->p_sum+=moldyn->p;
+ moldyn->mean_p=moldyn->p_sum/moldyn->total_steps;
+
+ /* pressure from 'absolute coordinates' virial */
+ virial=&(moldyn->virial);
+ v=virial->xx+virial->yy+virial->zz;
+ moldyn->gp=2.0*moldyn->ekin+v;
+ moldyn->gp/=(3.0*moldyn->volume);
+ moldyn->gp_sum+=moldyn->gp;
+ moldyn->mean_gp=moldyn->gp_sum/moldyn->total_steps;
+
+ return moldyn->p;
+}
+
+int energy_fluctuation_calc(t_moldyn *moldyn) {
+
+ /* assume up to date energies */
+
+ /* kinetic energy */
+ moldyn->k_sum+=moldyn->ekin;
+ moldyn->k2_sum+=(moldyn->ekin*moldyn->ekin);
+ moldyn->k_mean=moldyn->k_sum/moldyn->total_steps;
+ moldyn->k2_mean=moldyn->k2_sum/moldyn->total_steps;
+ moldyn->dk2_mean=moldyn->k2_mean-(moldyn->k_mean*moldyn->k_mean);
+
+ /* potential energy */
+ moldyn->v_sum+=moldyn->energy;
+ moldyn->v2_sum+=(moldyn->energy*moldyn->energy);
+ moldyn->v_mean=moldyn->v_sum/moldyn->total_steps;
+ moldyn->v2_mean=moldyn->v2_sum/moldyn->total_steps;
+ moldyn->dv2_mean=moldyn->v2_mean-(moldyn->v_mean*moldyn->v_mean);
+
+ return 0;
+}
+
+int get_heat_capacity(t_moldyn *moldyn) {
+
+ double temp2,ighc;
+
+ /* (temperature average)^2 */
+ temp2=moldyn->mean_t*moldyn->mean_t;
+ printf("[moldyn] specific heat capacity for T=%f K [J/(kg K)]\n",
+ moldyn->mean_t);
+
+ /* ideal gas contribution */
+ ighc=3.0*moldyn->count*K_BOLTZMANN/2.0;
+ printf(" ideal gas contribution: %f\n",
+ ighc/moldyn->mass*KILOGRAM/JOULE);
+
+ /* specific heat for nvt ensemble */
+ moldyn->c_v_nvt=moldyn->dv2_mean/(K_BOLTZMANN*temp2)+ighc;
+ moldyn->c_v_nvt/=moldyn->mass;
+
+ /* specific heat for nve ensemble */
+ moldyn->c_v_nve=ighc/(1.0-(moldyn->dv2_mean/(ighc*K_BOLTZMANN*temp2)));
+ moldyn->c_v_nve/=moldyn->mass;
+
+ printf(" NVE: %f\n",moldyn->c_v_nve*KILOGRAM/JOULE);
+ printf(" NVT: %f\n",moldyn->c_v_nvt*KILOGRAM/JOULE);
+
+ return 0;