nonbonded(1)

NAME
nonbonded - Compute non-bonded interactions empirically

DESCRIPTION

The program nonbonded computes various empirical terms for non-bonded interactions (electrostatic and damped dispersion, presently). It was initially developed to test various Hartree-Fock + empirical dispersion models. This is an experimental module and not meant for production use at this time. Gradients and second derivatives are available for empirical dispersion terms only.

REFERENCES

Empirical damped dispersion terms:

1.  Semiempirical GGA-Type Density Functional Constructed with a Long-Range Dispersion Correction, S. Grimme, J. Comput. Chem. 27, 1787-1799 (2006).

2.  Hartree-Fock Dispersion Probe of the Equilibrium Structures of Small Microclusters of Benzene and Naphthalene: Comparison with Second-Order Moeller-Plesset Geometries, C. Gonzalez, T. C. Allison, and E. C. Lim, J. Phys. Chem. A 105, 10583-10587 (2001).

3.  Evaluation of the Hartree-Fock Dispersion (HFD) Model as a Practical Tool for Probing Intermolecular Potentials of Small Aromatic Clusters: Comprison of the HFD and MP2 Intermolecular Potentials, C. Gonzalez and E. C. Lim, J. Phys. Chem. A 107, 10105-10110 (2003).

FILES REQUIRED
    input.dat          - Input file
    file32             - Checkpoint file containing molecular geometry

TEMPORARY FILES USED
    NONE

FILES UPDATED
    output.dat         - Output file

INPUT FORMAT

The following command-line arguments are available:

-i fname
    Gives the filename for the input file. Defaults to input.dat.

-o fname
    Gives the filename for the output file. Defaults to output.dat.

Additional input for this program is read from the file The following keywords are valid:

PARTIAL_CHARGES = double_array
    Partial charges on each atom, used for computation of empirical electrostatics. These contributions are included in the energy but not yet in gradients.

S6 = double
    Global scaling parameter for the damped dispersion terms. The values recommended by Grimme are 0.75 PBE, 1.2 BLYP, 1.05 B-P86, 1.0 TPSS, 1.05 B3LYP. Default is 1.0.

DAMP = boolean
    This boolean controls whether the dispersion terms are damped or not. This should be set to true (the default) except for debugging.

D_DMP = double
    Global damping exponent for damped dispersion terms. The larger this factor, the faster the dispersion interaction will be damped out as the interatomic distance decreases below the sum of the van der Waals radii. With Grimme's damping factor, the damped dispersion term is always 1/2 its undamped value when the atoms are at a distance equal to the sum of the van der Waals radii. For larger interatomic distances, the larger D_DMP, the faster the damping term approaches 1 (leaving dispersion undamped).

VDW_RADII = mixed array
    The user can specify custom van der Walls radii for use in the dispersion computation. The array VDW_RADII contains a list of atomic symbols and their associated van der Walls radii. Example: vdw_radii = (Ne 0.95 Ar 1.50) will set the van der Walls radii of all neon atoms to 0.95 and all argon atoms to 1.50.

C6 = mixed array
    The user can specify custom C6 coefficients for use in the dispersion computation. The array C6 contains a list of atomic symbols and their associated C6 coefficients. Example: C6 = (Ne 0.40 Ar 4.50) will set the C6 coefficients of all neon atoms to 0.40 and all argon atoms to 4.50.