NAME

     mp2r12  − calculates the MP2‐R12 energy in standard approxi‐
     mation A for closed‐shell systems.

DESCRIPTION

     The program mp2r12 determines  the  linear‐R12  second‐order
     Moller‐Plesset energy for closed‐shell systems.  Input inte‐
     grals must come from the restricted transformation available
     in the TRANSQT program.  Frozen orbitals are not allowed, as
     the  basis sets used in linear‐R12 computations employ basis
     sets with more than enough flexibility to describe core‐cor‐
     relation effects correctly.

REFERENCES

     Moller‐Plesset original paper:

     1.   C. Moller and M. S. Plesset, "Note on an  Approximation
          Treatment  for  Many‐Electron Systems", Phys. Rev., 46,
          618(1934).

     Linear R12 theory formulation:

     2.   W. Kutzelnigg and  W.  Klopper,  "Wave  functions  with
          terms linear in the interelectronic coordinates to take
          care  of  the correlation cusp.  I. General Theory", J.
          Chem. Phys., 94, 1985(1991).

     MP2‐R12/A programmable expressions:

     3.   W. Klopper, "Limiting values for Moller‐Plesset second‐
          order correlation energies  of  polyatomic  systems:  A
          benchmark  study  on  Ne, HF, H2O, N2, and He...He", J.
          Chem. Phys., 102, 6168(1995).

FILES REQUIRED

          input.dat
          FILE30
          FILE72        (electron repulsion integrals, produced by transqt)
          FILE79        (integrals of r12 operator, produced by transqt)
          FILE80        (integrals of [r12,T2] operator, produced by transqt)

FILES GENERATED

          output.dat

INPUT OPTIONS

     mp2r12 has the following options:

     PRINT_LVL = integer
          Determines the verbosity of the  printing  information.
          A  print  value of 0 gives minimal information, while 5
          gives debugging information (do NOT  use  print  levels
          above 3 for more than 20 basis functions).  The default
          is 0.

     TOLERANCE = integer
          This  gives  the  exponent  of the cutoff value for the
          elimination of two‐electron integrals from the list  of
          those  on  disk.  The default is 14, giving a cutoff of
          1e‐14.

     FROZEN_DOCC = int_array
          Number of frozen doubly‐occupied orbitals in each  sym‐
          metry block.  Default is a vector of zeroes.

     FROZEN_UOCC = int_array
          Number  of  frozen unoccupied orbitals in each symmetry
          block.  Default is a vector of zeroes.

     C_LIMIT = boolean
          Instead  of  using  variationally  optimized  C‐coeffi‐
          cients, use limiting values (1/2 for singlet pairs, 1/4
          for triplet pairs).  Default is false.