| real*8 function ENERG(S, L, PBC) | |
| integer*2 :: S(1:L, 1:L) | |
| integer*4 :: I, J, L | |
| integer*4 :: PBC(0:L+1) | |
| real*8 :: ENE | |
| ENE = 0.0d0 | |
| do I = 1, L | |
| do J = 1, L | |
| ENE = ENE - S(I, J)*S(PBC(I + 1), J) - S(I, J)*S(I, PBC(J + 1)) | |
| enddo | |
| enddo | |
| ENERG = ENE | |
| return | |
| endfunction |