diff --git a/src/ao_one_e_ints_periodic/EZFIO.cfg b/src/ao_one_e_ints_periodic/EZFIO.cfg
new file mode 100644
index 00000000..5dac91f7
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/EZFIO.cfg
@@ -0,0 +1,72 @@
+[ao_integrals_e_n]
+type: double precision
+doc: Nucleus-electron integrals in |AO| basis set
+size: (ao_basis.ao_num,ao_basis.ao_num)
+interface: ezfio
+
+[io_ao_integrals_e_n]
+type: Disk_access
+doc: Read/Write |AO| nucleus-electron attraction integrals from/to disk [ Write | Read | None ]
+interface: ezfio,provider,ocaml
+default: None
+
+
+[ao_integrals_kinetic]
+type: double precision
+doc: Kinetic energy integrals in |AO| basis set
+size: (ao_basis.ao_num,ao_basis.ao_num)
+interface: ezfio
+
+[io_ao_integrals_kinetic]
+type: Disk_access
+doc: Read/Write |AO| kinetic integrals from/to disk [ Write | Read | None ]
+interface: ezfio,provider,ocaml
+default: None
+
+
+[ao_integrals_pseudo]
+type: double precision
+doc: Pseudopotential integrals in |AO| basis set
+size: (ao_basis.ao_num,ao_basis.ao_num)
+interface: ezfio
+
+[io_ao_integrals_pseudo]
+type: Disk_access
+doc: Read/Write |AO| pseudopotential integrals from/to disk [ Write | Read | None ]
+interface: ezfio,provider,ocaml
+default: None
+
+
+[ao_integrals_overlap]
+type: double precision
+doc: Overlap integrals in |AO| basis set
+size: (ao_basis.ao_num,ao_basis.ao_num)
+interface: ezfio
+
+[io_ao_integrals_overlap]
+type: Disk_access
+doc: Read/Write |AO| overlap integrals from/to disk [ Write | Read | None ]
+interface: ezfio,provider,ocaml
+default: None
+
+
+[ao_one_e_integrals]
+type: double precision
+doc: Combined integrals in |AO| basis set
+size: (ao_basis.ao_num,ao_basis.ao_num) 
+interface: ezfio
+
+[io_ao_one_e_integrals]
+type: Disk_access
+doc: Read/Write |AO| one-electron integrals from/to disk [ Write | Read | None ]
+interface: ezfio,provider,ocaml
+default: Read
+
+
+[num_kpts]
+type: integer
+doc: Number of k-points
+interface: ezfio,provider,ocaml
+default: 1
+
+
diff --git a/src/ao_one_e_ints_periodic/NEED b/src/ao_one_e_ints_periodic/NEED
new file mode 100644
index 00000000..61d23b1e
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/NEED
@@ -0,0 +1,2 @@
+ao_basis
+pseudo
diff --git a/src/ao_one_e_ints_periodic/README.rst b/src/ao_one_e_ints_periodic/README.rst
new file mode 100644
index 00000000..48ec8d01
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/README.rst
@@ -0,0 +1,15 @@
+==================
+ao_one_e_integrals
+==================
+
+All the one-electron integrals in the periodic |AO| basis are here.
+
+Warning: this is incompatible with non-periodic |AOs|.
+
+The most important providers for usual quantum-chemistry calculation are:
+
+* `ao_kinetic_integrals` which are the kinetic operator integrals on the |AO| basis 
+* `ao_integrals_n_e` which are the nuclear-elctron operator integrals on the |AO| basis
+* `ao_one_e_integrals` which are the the h_core operator integrals on the |AO| basis
+
+
diff --git a/src/ao_one_e_ints_periodic/ao_one_e_ints.irp.f b/src/ao_one_e_ints_periodic/ao_one_e_ints.irp.f
new file mode 100644
index 00000000..27e17754
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/ao_one_e_ints.irp.f
@@ -0,0 +1,29 @@
+ BEGIN_PROVIDER [ complex*16, ao_one_e_integrals,(ao_num,ao_num)]
+&BEGIN_PROVIDER [ double precision, ao_one_e_integrals_diag,(ao_num)]
+  implicit none
+  integer :: i,j,n,l
+  BEGIN_DOC
+ ! One-electron Hamiltonian in the |AO| basis.
+  END_DOC
+
+  IF (read_ao_one_e_integrals) THEN
+     call ezfio_get_ao_one_e_ints_ao_one_e_integrals(ao_one_e_integrals)
+  ELSE
+        ao_one_e_integrals = ao_integrals_n_e + ao_kinetic_integrals
+
+        IF (DO_PSEUDO) THEN
+              ao_one_e_integrals += ao_pseudo_integrals
+        ENDIF
+  ENDIF
+
+  DO j = 1, ao_num
+    ao_one_e_integrals_diag(j) = real(ao_one_e_integrals(j,j))
+  ENDDO
+
+  IF (write_ao_one_e_integrals) THEN
+       call ezfio_set_ao_one_e_ints_ao_one_e_integrals(ao_one_e_integrals)
+       print *,  'AO one-e integrals written to disk'
+  ENDIF
+
+END_PROVIDER
+
diff --git a/src/ao_one_e_ints_periodic/ao_overlap.irp.f b/src/ao_one_e_ints_periodic/ao_overlap.irp.f
new file mode 100644
index 00000000..9c74091f
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/ao_overlap.irp.f
@@ -0,0 +1,136 @@
+BEGIN_PROVIDER [ complex*16, ao_overlap,(ao_num,ao_num) ]
+  implicit none
+  BEGIN_DOC  
+! Overlap between atomic basis functions:
+! :math:`\int \chi_i(r) \chi_j(r) dr)`
+  END_DOC
+  if (read_ao_integrals_overlap) then
+    call read_one_e_integrals_complex('ao_overlap', ao_overlap,&
+        size(ao_overlap,1), size(ao_overlap,2))
+    print *,  'AO overlap integrals read from disk'
+  else
+    print *, 'complex AO overlap integrals must be provided'
+  endif
+END_PROVIDER
+
+
+BEGIN_PROVIDER [ double precision, ao_overlap_abs,(ao_num,ao_num) ]
+  implicit none
+  BEGIN_DOC  
+! Overlap between absolute value of atomic basis functions:
+! :math:`\int |\chi_i(r)| |\chi_j(r)| dr)`
+  END_DOC
+  integer :: i,j
+  !$OMP PARALLEL DO SCHEDULE(GUIDED) &
+  !$OMP DEFAULT(NONE) &
+  !$OMP PRIVATE(i,j) &
+  !$OMP SHARED(ao_overlap_abs,ao_overlap,ao_num)
+  do j=1,ao_num
+   do i= 1,ao_num
+    ao_overlap_abs(i,j)= cdabs(ao_overlap(i,j))
+   enddo
+  enddo
+  !$OMP END PARALLEL DO
+END_PROVIDER
+
+BEGIN_PROVIDER [ complex*16, S_inv,(ao_num,ao_num) ]
+ implicit none
+ BEGIN_DOC
+! Inverse of the overlap matrix
+ END_DOC
+ call get_pseudo_inverse_complex(ao_overlap,size(ao_overlap,1),ao_num,ao_num,S_inv,size(S_inv,1))
+END_PROVIDER
+
+BEGIN_PROVIDER [ complex*16, S_half_inv, (AO_num,AO_num) ]
+
+  BEGIN_DOC
+!   :math:`X = S^{-1/2}` obtained by SVD
+  END_DOC
+
+  implicit none
+
+  integer                         :: num_linear_dependencies
+  integer                         :: LDA, LDC
+  double precision, allocatable   :: D(:)
+  complex*16, allocatable   :: U(:,:),Vt(:,:)
+  integer                         :: info, i, j, k
+  double precision, parameter     :: threshold_overlap_AO_eigenvalues = 1.d-6
+
+  LDA = size(AO_overlap,1)
+  LDC = size(S_half_inv,1)
+
+  allocate(         &
+    U(LDC,AO_num),  &
+    Vt(LDA,AO_num), &
+    D(AO_num))
+
+  call svd_complex(    &
+       AO_overlap,LDA, &
+       U,LDC,          &
+       D,              &
+       Vt,LDA,         &
+       AO_num,AO_num)
+
+  num_linear_dependencies = 0
+  do i=1,AO_num
+    print*,D(i)
+    if(abs(D(i)) <= threshold_overlap_AO_eigenvalues) then
+      D(i) = 0.d0
+      num_linear_dependencies += 1
+    else
+      ASSERT (D(i) > 0.d0)
+      D(i) = 1.d0/sqrt(D(i))
+    endif
+    do j=1,AO_num
+      S_half_inv(j,i) = (0.d0,0.d0)
+    enddo
+  enddo
+  write(*,*) 'linear dependencies',num_linear_dependencies
+
+  do k=1,AO_num
+    if(D(k) /= 0.d0) then
+      do j=1,AO_num
+        do i=1,AO_num
+          S_half_inv(i,j) = S_half_inv(i,j) + U(i,k)*D(k)*Vt(k,j)
+        enddo
+      enddo
+    endif
+  enddo
+
+
+END_PROVIDER
+
+BEGIN_PROVIDER [ complex*16, S_half, (ao_num,ao_num)  ]
+ implicit none
+ BEGIN_DOC
+ ! :math:`S^{1/2}`
+ END_DOC
+
+  integer :: i,j,k
+  complex*16, allocatable  :: U(:,:)
+  complex*16, allocatable  :: Vt(:,:)
+  double precision, allocatable  :: D(:)
+
+  allocate(U(ao_num,ao_num),Vt(ao_num,ao_num),D(ao_num))
+
+  call svd_complex(ao_overlap,size(ao_overlap,1),U,size(U,1),D,Vt,size(Vt,1),ao_num,ao_num)
+
+  do i=1,ao_num
+    D(i) = dsqrt(D(i))
+    do j=1,ao_num
+      S_half(j,i) = (0.d0,0.d0)
+    enddo
+  enddo
+
+  do k=1,ao_num
+      do j=1,ao_num
+        do i=1,ao_num
+          S_half(i,j) = S_half(i,j) + U(i,k)*D(k)*Vt(k,j)
+        enddo
+      enddo
+  enddo
+
+  deallocate(U,Vt,D)
+
+END_PROVIDER
+
diff --git a/src/ao_one_e_ints_periodic/aos_kpts.irp.f b/src/ao_one_e_ints_periodic/aos_kpts.irp.f
new file mode 100644
index 00000000..e44d3a23
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/aos_kpts.irp.f
@@ -0,0 +1,5 @@
+
+BEGIN_PROVIDER [integer, ao_num_per_kpt ]
+  implicit none
+  ao_num_per_kpt = ao_num / num_kpts
+END_PROVIDER
diff --git a/src/ao_one_e_ints_periodic/kin_ao_ints.irp.f b/src/ao_one_e_ints_periodic/kin_ao_ints.irp.f
new file mode 100644
index 00000000..ea84bd4f
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/kin_ao_ints.irp.f
@@ -0,0 +1,18 @@
+BEGIN_PROVIDER [complex*16, ao_kinetic_integrals, (ao_num,ao_num)]
+  implicit none
+  BEGIN_DOC
+  ! array of the priminitve basis kinetic integrals
+  !  \langle \chi_i |\hat{T}| \chi_j \rangle
+  END_DOC
+  
+  if (read_ao_integrals_kinetic) then
+    call read_one_e_integrals_complex('ao_kinetic_integrals', ao_kinetic_integrals,&
+        size(ao_kinetic_integrals,1), size(ao_kinetic_integrals,2))
+    print *,  'AO kinetic integrals read from disk'
+  else
+    print *, 'complex AO kinetic integrals must be provided'
+    stop
+  endif
+END_PROVIDER
+
+
diff --git a/src/ao_one_e_ints_periodic/pot_ao_ints.irp.f b/src/ao_one_e_ints_periodic/pot_ao_ints.irp.f
new file mode 100644
index 00000000..36b7f7ae
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/pot_ao_ints.irp.f
@@ -0,0 +1,28 @@
+BEGIN_PROVIDER [ complex*16, ao_integrals_n_e, (ao_num,ao_num)]
+  BEGIN_DOC
+  !  Nucleus-electron interaction, in the |AO| basis set.
+  !
+  !  :math:`\langle \chi_i | -\sum_A \frac{1}{|r-R_A|} | \chi_j \rangle`
+  END_DOC
+
+   if (read_ao_integrals_e_n) then
+    call read_one_e_integrals_complex('ao_ne_integral', ao_integrals_n_e,      &
+            size(ao_integrals_n_e,1), size(ao_integrals_n_e,2))
+     print *,  'AO N-e integrals read from disk'
+   else
+     print *, 'complex AO N-e integrals must be provided'
+     stop
+   endif
+END_PROVIDER
+
+BEGIN_PROVIDER [ double precision, ao_integrals_n_e_per_atom, (ao_num,ao_num,nucl_num)]
+  BEGIN_DOC
+! Nucleus-electron interaction in the |AO| basis set, per atom A.
+!
+! :math:`\langle \chi_i | -\frac{1}{|r-R_A|} | \chi_j \rangle`
+  END_DOC
+  print *, 'ao_nucl_elec_integral_per_atom not implemented for k-points'
+  stop
+
+END_PROVIDER
+
diff --git a/src/ao_one_e_ints_periodic/pot_ao_pseudo_ints.irp.f b/src/ao_one_e_ints_periodic/pot_ao_pseudo_ints.irp.f
new file mode 100644
index 00000000..243efdcb
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/pot_ao_pseudo_ints.irp.f
@@ -0,0 +1,25 @@
+BEGIN_PROVIDER [ double precision, ao_pseudo_integrals, (ao_num,ao_num)]
+  implicit none
+  BEGIN_DOC
+  ! Pseudo-potential integrals in the |AO| basis set.
+  END_DOC
+
+  if (read_ao_integrals_pseudo) then
+    call ezfio_get_ao_one_e_ints_ao_integrals_pseudo(ao_pseudo_integrals)
+    print *,  'AO pseudopotential integrals read from disk'
+  else
+
+    if (do_pseudo) then
+      print *, irp_here, 'Not yet implemented'
+      stop -1
+    endif
+  endif
+
+  if (write_ao_integrals_pseudo) then
+    call ezfio_set_ao_one_e_ints_ao_integrals_pseudo(ao_pseudo_integrals)
+    print *,  'AO pseudopotential integrals written to disk'
+  endif
+
+END_PROVIDER
+
+
diff --git a/src/ao_one_e_ints_periodic/test.irp.f b/src/ao_one_e_ints_periodic/test.irp.f
new file mode 100644
index 00000000..3519c17f
--- /dev/null
+++ b/src/ao_one_e_ints_periodic/test.irp.f
@@ -0,0 +1,3 @@
+program test
+ print *, ' hello'
+end