diff --git a/src/bitmask/track_orb.irp.f b/src/bitmask/track_orb.irp.f
index e907f73d..9c430467 100644
--- a/src/bitmask/track_orb.irp.f
+++ b/src/bitmask/track_orb.irp.f
@@ -30,47 +30,81 @@ subroutine initialize_mo_coef_begin_iteration
 end
 
 subroutine reorder_core_orb
- implicit none
- BEGIN_DOC
- ! TODO: modify for complex
-! routines that takes the current :c:data:`mo_coef` and reorder the core orbitals (see :c:data:`list_core` and :c:data:`n_core_orb`) according to the overlap with :c:data:`mo_coef_begin_iteration`
- END_DOC
- integer :: i,j,iorb
- integer :: k,l
- double precision, allocatable :: accu(:)
- integer, allocatable :: index_core_orb(:),iorder(:)
- double precision, allocatable :: mo_coef_tmp(:,:)
- allocate(accu(mo_num),index_core_orb(n_core_orb),iorder(mo_num))
- allocate(mo_coef_tmp(ao_num,mo_num))
-
- do i = 1, n_core_orb
-  iorb = list_core(i)
-  do j = 1, mo_num
-   accu(j) = 0.d0
-   iorder(j) = j
-   do k = 1, ao_num
-    do l = 1, ao_num
-     accu(j) += mo_coef_begin_iteration(k,iorb) * mo_coef(l,j) * ao_overlap(k,l)
+  implicit none
+  BEGIN_DOC
+  ! TODO: test for complex
+ ! routines that takes the current :c:data:`mo_coef` and reorder the core orbitals (see :c:data:`list_core` and :c:data:`n_core_orb`) according to the overlap with :c:data:`mo_coef_begin_iteration`
+  END_DOC
+  integer :: i,j,iorb
+  integer :: k,l
+  integer, allocatable :: index_core_orb(:),iorder(:)
+  double precision, allocatable :: accu(:)
+  integer :: i1,i2
+  if (is_periodic) then
+    complex*16, allocatable :: accu_c(:)
+    allocate(accu(mo_num),accu_c(mo_num),index_core_orb(n_core_orb),iorder(mo_num))
+    do i = 1, n_core_orb
+      iorb = list_core(i)
+      do j = 1, mo_num
+        accu(j) = 0.d0
+        accu_c(j) = (0.d0,0.d0)
+        iorder(j) = j
+        do k = 1, ao_num
+          do l = 1, ao_num
+            accu_c(j) += dconjg(mo_coef_begin_iteration_complex(k,iorb)) * &
+                         mo_coef_complex(l,j) * ao_overlap_complex(k,l)
+          enddo
+        enddo
+        accu(j) = -cdabs(accu_c(j))
+      enddo
+      call dsort(accu,iorder,mo_num)
+      index_core_orb(i) = iorder(1)
     enddo
-   enddo
-   accu(j) = -dabs(accu(j))
-  enddo
-  call dsort(accu,iorder,mo_num)
-  index_core_orb(i) = iorder(1)
- enddo
 
- double precision :: x
- integer :: i1,i2
- do j = 1, n_core_orb
-  i1 = list_core(j)
-  i2 = index_core_orb(j)
-  do i=1,ao_num
-    x = mo_coef(i,i1)
-    mo_coef(i,i1) = mo_coef(i,i2)
-    mo_coef(i,i2) = x
-  enddo
- enddo
-!call loc_cele_routine
-
- deallocate(accu,index_core_orb, iorder)
+    complex*16 :: x_c
+    do j = 1, n_core_orb
+      i1 = list_core(j)
+      i2 = index_core_orb(j)
+      do i=1,ao_num
+         x_c = mo_coef_complex(i,i1)
+         mo_coef_complex(i,i1) = mo_coef_complex(i,i2)
+         mo_coef_complex(i,i2) = x_c
+      enddo
+    enddo
+    !call loc_cele_routine
+   
+    deallocate(accu,accu_c,index_core_orb, iorder)
+  else
+    allocate(accu(mo_num),index_core_orb(n_core_orb),iorder(mo_num))
+   
+    do i = 1, n_core_orb
+      iorb = list_core(i)
+      do j = 1, mo_num
+        accu(j) = 0.d0
+        iorder(j) = j
+        do k = 1, ao_num
+          do l = 1, ao_num
+            accu(j) += mo_coef_begin_iteration(k,iorb) * mo_coef(l,j) * ao_overlap(k,l)
+          enddo
+        enddo
+        accu(j) = -dabs(accu(j))
+      enddo
+      call dsort(accu,iorder,mo_num)
+      index_core_orb(i) = iorder(1)
+    enddo
+   
+    double precision :: x
+    do j = 1, n_core_orb
+      i1 = list_core(j)
+      i2 = index_core_orb(j)
+      do i=1,ao_num
+         x = mo_coef(i,i1)
+         mo_coef(i,i1) = mo_coef(i,i2)
+         mo_coef(i,i2) = x
+      enddo
+    enddo
+    !call loc_cele_routine
+   
+    deallocate(accu,index_core_orb, iorder)
+  endif
 end
diff --git a/src/utils_periodic/qp2-pbc-diff.txt b/src/utils_periodic/qp2-pbc-diff.txt
index 75693491..dd8e69c2 100644
--- a/src/utils_periodic/qp2-pbc-diff.txt
+++ b/src/utils_periodic/qp2-pbc-diff.txt
@@ -14,9 +14,6 @@ ao_ints
 		[ double precision, ao_two_e_integral_schwartz,(ao_num,ao_num)  ]
 		compute_ao_integrals_jl
 
-mo_basis
-	reorder_core_orb: implement for periodic
-
 scf
 	finish ao_two_e_integral_{alpha,beta}_complex (need reverse index?)