 /*! \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
 */

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

        {
        unsigned int idx = d_group_members[group_idx];
   
        // read in the net force and calculate the acceleration
        float4 accel = tex1Dfetch(net_force_tex, idx);
        float mass = tex1Dfetch(pdata_mass_tex, idx);
