dboc - Online in the Cloud

PROGRAM:

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)

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