diff --git a/src/HF/GHF_search.f90 b/src/HF/GHF_search.f90
index e983ab5..b33c5b1 100644
--- a/src/HF/GHF_search.f90
+++ b/src/HF/GHF_search.f90
@@ -146,7 +146,7 @@ subroutine GHF_search(maxSCF,thresh,max_diis,guess_type,mix,level_shift,nNuc,ZNu
     call phLR_A(ispin,.false.,nBas2,nC,nO,nV,nR,nS,1d0,e,ERI_MO,Aph)
     call phLR_B(ispin,.false.,nBas2,nC,nO,nV,nR,nS,1d0,ERI_MO,Bph)
  
-    AB(:,:) = Aph(:,:) + Bph(:,:)
+    AB(:,:) = Aph(:,:) - Bph(:,:)
  
     call diagonalize_matrix(nS,AB,Om)
     Om(:) = 0.5d0*Om(:)