The Conductor-like Screening Model (COSMO)
(A. Klamt and G. Schüürmann, J. Chem. Soc. Perkin Trans. II 799-805 (1993))
is currently available for HF (RHF,UHF) and DFT (RKS,UKS) energy calculations and the corresponding gradients.
58 THE COSMO MODEL
The COSMO model is invoked by the COSMO card:
where option can be
It is recommended to change the default values for problematic cases only.
- size of the underlying basis grid. The value must satisfy:
(default = 1082; type integer).
- number of segments for non hydrogen atoms. The value must
(default = 92; type integer).
- the intersection seams of the molecular surface
are closed (1) or open (0) (default = 1; type integer).
- dielectric permittivity (default = -1.d0, which means
; type real)
- distance criteria for the -matrix setup.
Short range interactions (segment centre distances
< DISEX mean atomic diameter) are calculated using
the underlying basis grid. Long range interactions
are calculated via the segment centres (default = 10.d0; type float).
- factor used for outer cavity construction. The radii of the
outer cavity are defined as:
(default = 0.85d0; type float)
- phase offset of coordinate randomization (default = 0.d0; type float)
- amplitude factor of coordinate randomization
(default = 1.0d-5; type float)
- additional radius for cavity construction (default = -1d0, the optimized H radius is used;
- maximal number of surface segments (default = -1, will be estimated; type integer).
By default the program uses optimized radii if existent and 1.17vdW radius
The optimized radii [Å] are: H=1.30, C=2.00, N=1.83, O=1.72, F=1.72, S=2.16, Cl=2.05, Br=2.16, I=2.32.
Own proposals can be given directly subsequent to the cosmo card:
where the radius has to be given in Å.
The COSMO output file will be written after every converged SCF calculation. The segment charges and potentials are corrected by the outlying charge correction. For the total charges and energies corrected and uncorrected values are given.
The normal output file contains uncorrected values only. It is recommended to use the corrected values from the output file.
It is recommended to use optimizer that operates with gradients exclusively. Line search techniques that use energies tends to fail, because of the energy discontinuities which may occur due to a reorganization of the segments after a geometry step. For the same reasons numerical gradients are not recommended.