Keyword MCPS

This keyword specifies the use of model core potentials (MCPS). Its syntax is very similar to that for the ECPS keyword.
Options:

$<$MCP$>$

MCP string $<$MCP$>$ defines the global model core potentials. If absent, an all-electron calculation is assumed by default.

Different MCPs can be assigned to individual atoms by the atomic symbol (e.g. Au1) or to atom groups by the element symbol (e.g. Au). The global MCP is used for all atoms for which MCPs are not specified explicitly. Simultaneous use of ECPs and MCPs for the same atomic center is forbidden. If MCPS is not specified for an atom but the substring "MCP" is present in the basis set definition of the keyword BASIS, then an MCP of the same name will be assigned automatically to that atom. The assignment of the MCP by atomic symbols, element symbols, and global MCPS definition follows the usual deMon2k hierarchy (highest to lowest):

$<$atomic symbol$>$
$<$element symbol$>$
$<$global MCPS$>$
$<$basis set name$>$

Thus, as in the case of ECPS, any MCPS definition for an atom can be overridden by the explicit assignment of the MCP using the atomic symbol. For example, in a system containing two copper atoms, e.g. linked to an organic ligand, the following MCPS definition,

 MCPS (MCP|LK)
 Cu   (MCP17|LK)
 Cu1  (RMCP17|LK)

assigns the 17-electron quasi-relativistic MCP from Lovallo and Klobukowski [152,153] denoted by (RMCP17$\vert$LK) to copper atom Cu1, the 17-electron non-relativistic MCP by the same authors, denoted by (MCP17$\vert$LK), to other copper atoms, and the globally defined (MCP$\vert$LK) non-relativistic MCP to any atom of other types that is present in the ligand. The file MCPS contains the MCPs from Lovallo and Klobukowski [152,153] in the deMon2k format. Figure 9 shows the elements for which MCPS are available in the MCPS file.

Figure 9: Lovallo-Klobukowski MCPs (top) and RMCPs (bottom) that are available in the MCPS file of deMon2k.

Specifying only the keyword MCPS and not specifying the corresponding valence basis set leads to a situation in which the default all-electron DZVP basis set is used in combination with the specified model core potentials. Therefore it is handy to define the model core potential and the corresponding valence basis set at the same time with the keyword BASIS. The keyword MCPS should then be used only to define a model core potential different from the one automatically invoked by the specified basis set. In the following example

 BASIS (MCP|LK)
 MCPS       
 Cu   (MCP17|LK)
 Cu1  (RMCP17|LK)

the explicit specification of the model core potential by the MCPS keyword overrides the global model core potential invoked with the keyword BASIS. The model core potentials can also be specified in the input file using the format

 MCPS
 SYMBOL Read ELECTRONS
 LS NLS
 N  K
    EXPONENT  COEFFICIENT
       :           :
    EXPONENT  COEFFICIENT
 N  K  F
    EXPONENT  COEFFICIENT
       :           :
    EXPONENT  COEFFICIENT

Here SYMBOL can be an element or atomic symbol, ELECTRONS is an integer number specifying the number of valence electrons, LS is the number of local shells in the model potential, and NLS is the number of non-local (core) shells. All local shells are loaded first. For each local shell, N represents the radial power and K the degree of contraction. For non-local shells, N represents the principal quantum number, K is the degree of contraction, and F is the energy weight-factor of the non-local projector of this shell. The exponents and contraction coefficients are listed in free format under the MCP block definition line, one line for each Gaussian (EXPONENT and COEFFICIENT).