About PBC:

Tuckerman (* in Appendix B, Eq B.9 provides the general algorithm for the minimum image convention:

  h := [a, b, c], a=(a1,a2,a3), ... (the matrix of box vectors)

  r_ij := r_i - r_j                 (difference vector)

  s_i = h^{-1} r_i  

  s_ij = s_i - s_j

  s_ij

About PBC:

Tuckerman (* in Appendix B, Eq B.9 provides the general algorithm for the minimum image convention:

  h := [a, b, c], a=(a1,a2,a3), ... (the matrix of box vectors)

  r_ij := r_i - r_j                 (difference vector)

  s_i = h^{-1} r_i  

  s_ij = s_i - s_j

  s_ij

thanks sir... now realized that i hv to think in different way .... i.e in terms of  vector...