void find_core_electrons_PBC(float *R[], int numElec, float I[], int firstIon, int lastIon, float rcut, float L[], float Linv[], int2 *pairs[], float *dist[], int numPairs[], int numWalkers)
void find_core_electrons(float *R[], int numElec, float I[], int firstIon, int lastIon, float rcut, int2 *pairs[], float *dist[], int numPairs[], int numWalkers)