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= First-order energy scan: MC/DC case =
Basis restrictions:
  * Main basis must be type MC with spherical GTOs
  * Auxiliary basis must be type DC with spherical GTOs.

{{{#!wiki  important
Important

The full CamCASP input file for [[AJMPublic/camcasp/energy-scan-module/py2-e1-mc-dc-example|the pyridine dimer scan with MC main and DC auxiliary basis sets is located here.]]
}}}

Explanation of key aspects of the input file:
=== Definition of the molecules ===
We need to define the molecules with an MC main basis (easy) and a DC auxiliary basis (not hard, but not obvious). Further, the order of the sites in the auxiliary basis sets of the two molecules must be the same. This is best illustrated with a diagram:
{{{
  For two molecules A and B with sites a1,a2,a3 and b1,b2 (say), we must define
  the basis sets as follows:
  
  A                        B
     Main   Aux                Main  Aux
     a1     a1                 b1    a1
     a2     a2                 b2    a2
     a3     a3                       a3
            b1                       b1
            b2                       b2
}}}

The coordinates used in these molecule definitions must be those of the molecules in their reference geometries. In the pyridine dimer example, the two molecules are identical, and have the following coordinates:

[[attachment:pyridine dimer molecule definitions]]

{{{
MOLECULE pyridine1 at 0.0 0.0 0.0
   Charge    0
   Echo No
   Hessian format SAPT2006
   MO-file vectA-daTZ.data Format BINARY
   IP     0.500000 a.u.
   Basis Main
      Spherical
      Units Bohr
      Format GAMESS
      Type MC
      H1         1.0       -3.87454677       2.40829326       0.00000000  TYPE H1
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/H
      ---
      H2         1.0       -4.05745524      -2.27382980       0.00000000  TYPE H2
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/H
      ---
      H3         1.0        0.00000000      -4.70080300       0.00000000  TYPE H3
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/H
      ---
...
      C5         6.0        2.14372406       1.30476509       0.00000000  TYPE C1
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/C
      ---
   End
   Basis Aux
      Spherical
      Units Bohr
      Format TURBOMOLE
      Type DC
      H1         1.0       -3.87454677       2.40829326       0.00000000  TYPE H1
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H2         1.0       -4.05745524      -2.27382980       0.00000000  TYPE H2
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H3         1.0        0.00000000      -4.70080300       0.00000000  TYPE H3
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
...
      C5         6.0        2.14372406       1.30476509       0.00000000  TYPE C1
        Limit G  MIN-S-EXP = 0.0
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/C
      ---

      H1         1.0       -3.87454677       2.40829326       0.00000000  TYPE H1
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H2         1.0       -4.05745524      -2.27382980       0.00000000  TYPE H2
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H3         1.0        0.00000000      -4.70080300       0.00000000  TYPE H3
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
...
      C5         6.0        2.14372406       1.30476509       0.00000000  TYPE C1
        Limit G  MIN-S-EXP = 0.0
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/C
      ---
   End
END

MOLECULE pyridine2 at 0.0 0.0 0.0
   Charge    0
   Echo No
   Hessian format SAPT2006
   MO-file vectA-daTZ.data Format BINARY
   IP     0.500000 a.u.
   Basis Main
      Spherical
      Units Bohr
      Format GAMESS
      Type MC
      H1         1.0       -3.87454677       2.40829326       0.00000000  TYPE H1
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/H
      ---
      H2         1.0       -4.05745524      -2.27382980       0.00000000  TYPE H2
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/H
      ---
      H3         1.0        0.00000000      -4.70080300       0.00000000  TYPE H3
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/H
...
      ---
      C5         6.0        2.14372406       1.30476509       0.00000000  TYPE C1
        #include-camcasp basis/gamess_us/d-aug-cc-pVTZ/C
      ---
   End
   Basis Aux
      Spherical
      Units Bohr
      Format TURBOMOLE
      Type DC
      H1         1.0       -3.87454677       2.40829326       0.00000000  TYPE H1
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H2         1.0       -4.05745524      -2.27382980       0.00000000  TYPE H2
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H3         1.0        0.00000000      -4.70080300       0.00000000  TYPE H3
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
...
      C5         6.0        2.14372406       1.30476509       0.00000000  TYPE C1
        Limit G  MIN-S-EXP = 0.0
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/C
      ---

      H1         1.0       -3.87454677       2.40829326       0.00000000  TYPE H1
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H2         1.0       -4.05745524      -2.27382980       0.00000000  TYPE H2
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
      H3         1.0        0.00000000      -4.70080300       0.00000000  TYPE H3
        Limit G  MIN-S-EXP =  0.000
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/H
      ---
...
      C5         6.0        2.14372406       1.30476509       0.00000000  TYPE C1
        Limit G  MIN-S-EXP = 0.0
        #include-camcasp basis/auxiliary/aug-cc-pVTZ/C
      ---
   End
END
}}}
Notice the following:
  * The two molecules are identical! They share the same MOs and the same reference geometry.
  * That means that the auxiliary basis set for each molecule contains two sets of apparently identical sites. For example, there are two H1 sites, and they are located at the same point in space.
  * This is not a problem: In the next set of commands we will pair each molecule with the other. This will allow CamCASP to treat the second set of sites as belonging to the partner molecule, and CamCASP will get the actual coordinates of those sites from the partner molecule.

=== Partner molecules ===
This is how we tell CamCASP that each molecule has a partner that will be used to determine the position of the dummy sites in the auxiliary basis set:

[[attachment:Partner site specification]]

{{{
Edit pyridine1
  Partner-Monomer = pyridine2
  Update Geometry
End

Edit pyridine2
  Partner-Monomer = pyridine1
  Update Geometry
End
}}}
After these commands the second set of sites in the auxiliary basis definition of pyridine1 will be paired with the atomic sites of pyridine2, and the first set of sites in the auxiliary basis definition of pyridine2 will be paired with the atomic sites of pyridine1. 
            
=== DF and DF-INT settings ===

[[attachment:DF and DF-INT settings]]

{{{
SET DF
  REDO-DF-ON-ROTATION   True
END

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

Set DF-INTS
  DF-TYPE-MONOMER  OO
  DF-TYPE-DIMER    OO
End
}}}

We use the SET blocks shown above to alter the default settings in the CamCASP code for this calculation:
  * ''REDO-DF-ON-ROTATION   True'' : When using DC-type auxiliary basis sets, the density-fitting step needs to be re-done for every new dimer configuration. This is because the positions of the sites in the auxiliary basis changes. So we set this flag. If set to ''False'', CamCASP will trap the error.
  * Next we set the density-fitting parameters for this calculation. Since we are after first-order energies only, set the type of density-fitting to ''OO'', i.e., fit occupied-occupied pairs of MOs only.
  * We do something similar for the DF-Integral module by informing it that the default type of density-fitting will be ''OO''. If this is not done, the code will use the ''OV'' default (which includes ''OO'').  

=== Energy settings ===
Next set the ''Integral switch = 1'' in the energy modules. This causes the code to use the more accurate integrals.

[[attachment:Integral switch settings]]

{{{
Set E1elst
  Integral switch = 1
End
Set E1exch
  Integral switch = 1
End
}}}

{{{#!wiki  important
Important

//Integral Accuracy//: When the DF is done accurately - here when the DC-aux basis is used - then it seems that we must use 1-electron integrals computed as accurately as is possible. So we use ''Integral switch = 1''. But if we use a relatively poor DF (as is the case with the MC-MC case when we use the MC-aux basis type), then we need to rely on an error cancellation in the terms that appear in $E^{(1)}_{\rm elst}$. So we need to use  ''Integral switch = 0''.
}}}

=== ENERGY-SCAN commands ===
Finally we set the ''ENERGY-SCAN'' commands:

[[attachment:Energy-Scan commands]]

{{{
Begin Energy-Scan
  Probe pyridine1 with pyridine2
  Energy  E1elst & E1exch
  Units Bohr
  ! Debug
  Points
     File pyr2-scan.geom
  ---
End
}}}
Some comments:
  * The ''Probe'' line tells the energy scan module that pyridine1 is going to be probed by pyridine2. This has the effect of keeping pyridine1 fixed at its reference geometry, while the geometry parameters contained in the [[ajm:camcasp:energy-scan-module:pyr2-geometry-file|pyr2-scan.geom file]] will be applied to pyridine2. 
  * The geometry file will be included so it must be present.

The geometries are in file:

[[attachment:pyr2-scan.geom]]

{{{
  UNITS BOHR DEGREE
  Skip-First-Column
  ! POINTS    10
  ! LABELS INDEX   Rx            Ry            Rz            alpha         Nx            Ny            Nz
       1   0.136313E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       2   0.119628E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       3   0.122605E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       4   0.134372E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       5  -0.916710E+01   0.000000E+00   0.529263E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       6  -0.972145E+01   0.000000E+00   0.561268E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       7  -0.722802E+01   0.000000E+00   0.417310E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       8  -0.975164E+01   0.000000E+00   0.563011E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       9   0.000000E+00  -0.126520E+02   0.326673E+01   0.600000E+02   0.000000E+00  -0.100000E+01   0.000000E+00
      10   0.000000E+00  -0.108432E+02   0.279972E+01   0.600000E+02   0.000000E+00  -0.100000E+01   0.000000E+00
}}}

=== Output ===
Here is part of the output of the above calculation. I have used ''REDO-DF-ON-ROTATION FALSE'' to demonstrate how CamCASP traps and corrects this error.

[[attachment:pyridine dimer scan MC_DC]]

{{{

Begin Energy-Scan
  Probe pyridine1 with pyridine2
  Energy  E1elst & E1exch
  Units Bohr
  ! Debug
  Points
     File pyr2-scan.geom
  ---
UNITS BOHR DEGREE
POINTS
  Skip-First-Column
  ! POINTS    10
  ! LABELS INDEX   Rx            Ry            Rz            alpha         Nx            Ny            Nz
       1   0.136313E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       2   0.119628E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       3   0.122605E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       4   0.134372E+02   0.000000E+00   0.000000E+00   0.180000E+03   0.100000E+01   0.000000E+00   0.000000E+00
       5  -0.916710E+01   0.000000E+00   0.529263E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       6  -0.972145E+01   0.000000E+00   0.561268E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       7  -0.722802E+01   0.000000E+00   0.417310E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       8  -0.975164E+01   0.000000E+00   0.563011E+01   0.180000E+03  -0.707107E+00   0.000000E+00  -0.707107E+00
       9   0.000000E+00  -0.126520E+02   0.326673E+01   0.600000E+02   0.000000E+00  -0.100000E+01   0.000000E+00
      10   0.000000E+00  -0.108432E+02   0.279972E+01   0.600000E+02   0.000000E+00  -0.100000E+01   0.000000E+00
---
End
 WARNING: ENERGY-SCAN with a dimer auxiliary basis needs to have:
    REDO-DF-ON-ROTATION = .true.
 Setting this here, but it should be set in the DF module.
 WARNING: in subroutine energy_scan_parser line          719
 Setting REDO-DF-ON-ROTATION=.true.
 INFO =            1
 Number of points =    10
      Rx         Ry         Rz         alpha      Nx         Ny         Nz              E(1)elst        E(2)ind         E(2)disp        E(1)exch        E(2)exind       E(2)exdisp      TotOverlap      Eelst-MP        Eind-MP         Edisp-MP        Delta
            BOHR       BOHR       BOHR    DEGREES        ---        ---        ---          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL          KJ/MOL
 ------------------------------------------------------------------------------
    1  13.6313000   0.0000000   0.0000000 180.0000000   1.0000000   0.0000000   0.0000000   8.1208599E-01   0.0000000E+00   0.0000000E+00   4.7754761E-01   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    2  11.9628000   0.0000000   0.0000000 180.0000000   1.0000000   0.0000000   0.0000000   6.5729689E-01   0.0000000E+00   0.0000000E+00   1.0251847E+01   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    3  12.2605000   0.0000000   0.0000000 180.0000000   1.0000000   0.0000000   0.0000000   1.0223858E+00   0.0000000E+00   0.0000000E+00   5.9771538E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    4  13.4372000   0.0000000   0.0000000 180.0000000   1.0000000   0.0000000   0.0000000   8.8945294E-01   0.0000000E+00   0.0000000E+00   6.8629620E-01   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    5  -9.1671000   0.0000000   5.2926300 180.0000000  -0.7071070   0.0000000  -0.7071070  -1.1622463E+00   0.0000000E+00   0.0000000E+00   3.5327413E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    6  -9.7214500   0.0000000   5.6126800 180.0000000  -0.7071070   0.0000000  -0.7071070  -5.4924311E-01   0.0000000E+00   0.0000000E+00   1.2086289E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    7  -7.2280200   0.0000000   4.1731000 180.0000000  -0.7071070   0.0000000  -0.7071070  -4.5123293E+01   0.0000000E+00   0.0000000E+00   1.4932393E+02   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    8  -9.7516400   0.0000000   5.6301100 180.0000000  -0.7071070   0.0000000  -0.7071070  -5.3223392E-01   0.0000000E+00   0.0000000E+00   1.1407984E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
    9   0.0000000 -12.6520000   3.2667300  60.0000000   0.0000000  -1.0000000   0.0000000  -2.4924072E+00   0.0000000E+00   0.0000000E+00   9.7557631E-01   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
   10   0.0000000 -10.8432000   2.7997200  60.0000000   0.0000000  -1.0000000   0.0000000  -9.6588506E+00   0.0000000E+00   0.0000000E+00   2.0501909E+01   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00   0.0000000E+00
------------------------------------------------------------------------------
  Scan results will be written in file: energy_file.dat

}}}