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NAME

       dboc - Diagonal Born-Oppenheimer Correction using HF and CI wave functions.

DESCRIPTION

       The program dboc computes Diagonal Born-Oppenheimer Correction (DBOC) using HF and CI wave
       functions.

REFERENCES

       "Cartesian" DBOC formula (aka Born-Handy-Pulay formula):

       1.     N. C. Handy, J. Yamaguchi, and H. F. Schaefer, J. Chem. Phys. 84, 4481 (1986).

       Justification for the "Cartesian" DBOC formula:

       1.     W. Kutzelnigg, Mol. Phys. 90, 909 (1997).

       Finite-difference formulation of DBOC at CI level

       1.     E. F. Valeev and C. D. Sherrill, J. Chem. Phys. 118, 3921 (2003).

INPUT FORMAT

       The following keywords are valid:

       WFN = string
              Specifies the type of wave function desired. The only valid entries at the  present
              are SCF and DETCI. There is no default.

       REFERENCE = string
              Specifies  the type of orbitals used for the single-determinant reference function.
              Valid choices are RHF, ROHF, and UHF.  There is no default.

       PRINT = integer
              Determines the verbosity of the output.  A  value  of  0  (the  default)  specifies
              minimal printing.

       :DBOC:DISPLACEMENT = real
              Determines the finite difference step (in a.u.). The default is 0.0005 a.u.

       :DBOC:DISP_PER_COORD = integer
              Determines  the number of displacements for each coordinate. Set it to 2 to compute
              DBOC  with  standard  accuracy  (enough  significant  digits  for  up   to   second
              derivatives;  DBOC  accurate to square of displacement size), and 4 to compute DBOC
              with improved accuracy (DBOC accurate to the fourth power  of  displacement  size).
              The default is 2.

       ISOTOPES = string_vector
              Specifies which isotope to use for each atom. Each string should specify an isotope
              label as defined in include/masses.h. By default, most abundant isotopes  are  used
              for each element.

       :DBOC:COORDS = vector
              This  keyword  should only be used by advanced users who are familiar with how DBOC
              is evaluated by finite differences.   The  keyword  may  be  used  to  specify  the
              cartesian  nuclear  coordinates  to  use  in  the  sum  expression  for DBOC, their
              respective coefficients, and  whether  they  are  symmetric  or  nonsymmetric  with
              respect  displacements.   dboc  can  use  symmetry  to  minimize the number of wave
              function computations.  Hence  this  keyword  need  only  be  used  for  diagnostic
              purposes  or  when  displacements  along  different  coordinates  need  to  be  run
              separately (e.g.  require  different  occupation  vectors).   The  value  for  this
              keyword  is  an array of 3 element vectors. The first element of each vector is the
              index of the cartesian coordinate which to include into the sum. The second element
              is  a  real  coefficient  for the respective term in the DBOC expression. The third
              element is a string that can take two values, symm and nonsymm, which indicate that
              the  coordinate  is  symmetric  or  nonsymmetric  with  respect  to  displacements,
              respectively.  Indices are C-style, i.e. from 0 to 3*natom-1.

                                          30 August, 2003                                 dboc(1)