Gaussian 03 manual keywords

Link atoms are necessary when covalent bonding exists between atoms in different layers in order to saturate the otherwise dangling bonds. Note : All link atoms must be specified by the user.

Gaussian 03 does not define them automatically or provide any defaults. The bonded-to parameter specifies which atom the current atom is to be bonded to during the higher-level calculation portion. If it is omitted, Gaussian will attempt to identify it automatically.

In general, Gaussian 03 determines bond distances between atoms and their link atoms by scaling the original bond distance i. However, you can also specify these scale factors explicitly. For a two-layer calculation, the scale factors specify the link atom bond distance in the model system when calculated at the low and high levels respectively. All of these scale factors correspond to the g-factor parameter as defined in reference [ ], extended to allow separate values for each ONIOM calculation level.

For a two-layer ONIOM, if only one parameter is specified, then both scale factors will use that value. For a three-layer ONIOM, if only one parameter is specified, then all three scale factors will use that value; if only two parameters are specified, then the third scale factor will use the second value.

If a scale parameter is explicitly set to 0. Thus, if you want to change only the second scale factor model system calculated at the medium level , then you must explicitly set the first scale factor to 0. In this case, for a three-layer ONIOM, the third scale factor will have the same value as the second parameter unless it is explicitly assigned a non-zero value i. When only a single value pair is specified, all levels will use those values. If two pairs of values are included, then the third pair defaults to the same values as in the second pair.

If the final pair is omitted for an S-value job, it defaults to the values for the real system at the low level. Thus, when only a subset of the six or nine pairs are specified, the charge and spin multiplicity items default according to the following scheme, where the number in each cell indicates which pair of values applies for that calculation in the corresponding :circumstances:. NoEmbedCharge is the default. MK Specifies that Merz-Kollman-Singh see Population approximate charges be used during geometry optimization microiterations with electronic embedding.

It is the default. Specifies scaling parameters for MM charges during electronic embedding in the QM calculations. The integers are multiplied by 0.

MobGrd is the default. MobHss is the default. FMM is the default. BiCGS Set the iterative algorithm to a stabilized biconjugate gradient. The DIIS option is not allowed with this keyword, and the algorithm defaults to Jacobi when it is used. CGS Set the iterative algorithm to a squared conjugate gradient.

This is the default for CPCM calculations. The ICOMP keyword, formerly used to specify the charge compensation mode, is no longer needed and is deprecated. By default, the program builds up the cavity using the United Atom UA0 model, i. There are three UA models available see below. The cavity can be extensively modified in the PCM input section: putting spheres around specified hydrogens, changing sphere parameters and the general cavity topology, adding extra spheres to the cavity built by default, and so on.

The whole molecular cavity can be also provided by the user in the input section. Available models and sets are:. Hydrogens have individual spheres explicit hydrogens. The default value is 1. Available options are:. The surface is generated by the atomic or group spheres and by the spheres created automatically to smooth the surface "added spheres".

This is the default for electrostatic contribution. VDW : Van der Waals surface. Uses unscaled atomic radii and skip the generation of "added spheres" to smooth the surface. The modified spheres can be indicated in the PCM input using the following format:. Parameters of the spheres can be indicated using the following format:. SymmCav is the default. Decreasing this index results in a smaller number of added spheres. The default value is 0. Increasing this value results in a smaller number of added spheres.

The following table lists the valence polarization functions present for the various atoms included in these basis sets:. However, the elements He, Mg, Li, Be, and Na do not have diffuse functions defined within these basis sets.

The MidiX keyword is used to request this basis set. EPR-III is a triple-zeta basis set including diffuse functions, double d-polarizations and a single set of f-polarization functions. The latter three keyword forms have an additional 1, 2 or three polarization functions for each function in the normal UGBS basis set i.

For example, the AUG-cc-pVTZ basis places one s, one d, and one p diffuse functions on hydrogen atoms, and one d, one p, one d, and one f diffuse functions on B through Ne and Al through Ar. Adding a single polarization function to G i. Similarly, adding a diffuse function to the G basis set will produce one s, one p, and one d diffuse functions for third-row atoms.

When a frozen-core calculation is done using the D95 basis, both the occupied core orbitals and the corresponding virtual orbitals are frozen.

The following table lists polarization and diffuse function availability and the range of applicability for each built-in basis set in Gaussian 03 :. Cartesian f functions , respectively. These keywords also apply to all higher functions g and beyond. Other basis sets may also be input to the program using the ExtraBasis and Gen keywords.

See the individual descriptions of these keywords later in this chapter for details. Gaussian users should be aware of the following points concerning pure vs.