         return error;
         
     // run the kernel
-    gpu_nvt_step_two_kernel<<< grid, threads >>>(pdata, d_group_members, group_size, d_net_force, Xi, deltaT);
+    gpu_nvt_step_two_kernel<<< grid, threads >>>(pdata, d_group_members, group_size, Xi, deltaT);
     
     if (!g_gpu_error_checking)
         {

/*! \param pdata Particle Data to step forward in time
    \param d_group_members Device array listing the indicies of the mebers of the group to integrate
    \param group_size Number of members in the group
    \param d_net_force Net force on each particle
    \param Xi current value of the NVT degree of freedom Xi
    \param deltaT Amount of real time to step forward in one time step
*/

void gpu_nvt_step_two_kernel(gpu_pdata_arrays pdata,
                             unsigned int *d_group_members,
                             unsigned int group_size,
                             float Xi,
                             float deltaT)
    {
