! This is important as it save a lot of computer time
! As both the main and auxiliary basis sets are type MC, 
! all objects, including the DF solution matrices can be 
! rotated with the molecules. So no re-calculations are needed.
 
SET DF
  REDO-DF-ON-ROTATION   False
END
 
! Various DF parameters. 
 
SET DF
  Molecule pyridine1
  Type OO
  Eta = 0.0
  Lambda = 0.0
  Gamma = 0.0
  Print only normalization constraints
  Solver LU
END
SET DF
  Molecule pyridine2
  Type OO
  Eta = 0.0
  Lambda = 0.0
  Gamma = 0.0
  Print only normalization constraints
  Solver LU
END
 
! Only occupied-occupied (OO) type integrals are needed.
! This saves computer time. The default is to compute 
! integrals in the OV and VV spaces too. Not needed for
! first-order energies.
 
Set DF-INTS
  DF-TYPE-MONOMER  OO
  DF-TYPE-DIMER    OO
End
 
! Set the integral switches in the energy modules. 
! Switch = 1 causes the code to compute the overlap and nuclear
! integrals without density-fitting (i.e. they are more accurate), but this introduces
! a large error in E(1)elst as there is no error cancellation. 
! For some reason this error cancellation is needed when we use an MC-type
! aux basis. So here we use switch = 0 to force CamCASP to use the 1-electron
! integrals with density-fitting. This results in more accurate E(1)elst, but
! bear in mind that E(1)elst with an MC-type main basis will never be 
! accurate enough.
 
Set E1elst
  Integral switch = 0
End
Set E1exch
  Integral switch = 0
End
 
Begin Energy-Scan
  Probe pyridine1 with pyridine2
  Energy  E1elst & E1exch
  Units Bohr
  ! Debug
  #include pyr2-scan.geom
End