diff --git a/quad10/fenomens/lab/p2/energ.f90 b/quad10/fenomens/lab/p2/energ.f90
new file mode 100644
index 0000000..4ee8508
--- /dev/null
+++ b/quad10/fenomens/lab/p2/energ.f90
@@ -0,0 +1,14 @@
+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