From 39d58d9eb5fc46eca629e02733b73775d8b3f887 Mon Sep 17 00:00:00 2001
From: pfloos <pierrefrancois.loos@gmail.com>
Date: Wed, 8 Nov 2023 22:59:13 +0100
Subject: [PATCH] AO <-> MO modifs

---
 src/AOtoMO/MOtoAO_transform_GHF.f90 | 35 +++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 src/AOtoMO/MOtoAO_transform_GHF.f90

diff --git a/src/AOtoMO/MOtoAO_transform_GHF.f90 b/src/AOtoMO/MOtoAO_transform_GHF.f90
new file mode 100644
index 0000000..9f91884
--- /dev/null
+++ b/src/AOtoMO/MOtoAO_transform_GHF.f90
@@ -0,0 +1,35 @@
+subroutine MOtoAO_transform_GHF(nBas2,nBas,S,Ca,Cb,B,A)
+
+! Perform MO to AO transformation of a matrix A for a given metric S
+! and coefficients c
+
+  implicit none
+
+! Input variables
+
+  integer,intent(in)            :: nBas2
+  integer,intent(in)            :: nBas
+  double precision,intent(in)   :: S(nBas,nBas)
+  double precision,intent(in)   :: Ca(nBas,nBas2)
+  double precision,intent(in)   :: Cb(nBas,nBas2)
+  double precision,intent(in)   :: B(nBas2,nBas2)
+
+! Local variables
+
+  double precision,allocatable  :: Sc(:,:)
+
+! Output variables
+
+  double precision,intent(inout):: A(nBas,nBas)
+
+! Memory allocation
+
+  allocate(Sc(nBas,nBas2))
+
+  Sc = matmul(S,Ca)
+  A = matmul(Sc,matmul(B,transpose(Sc)))
+
+  Sc = matmul(S,Cb)
+  A = A + matmul(Sc,matmul(B,transpose(Sc)))
+
+end subroutine