6.4 Details about supplying inner-core electron density for the wavefunctions involving pseudopotential¶
In Section 2.5, the characteristics and the meaning of electron density function (EDF) have been introduced. EDF information is used to represent the inner-core density replaced by pseudopotential, so that for the wavefunctions involving pseudopotential, the result of the wavefunction analyses that purely based on electron density can be almost exactly identical to full-electron wavefunction.
When the input file you used contains GTF information, and meantime some atoms utilized pseudopotential, Multiwfn automatically finds proper GTF information from built-in EDF library for these atoms. The built-in EDF library was developed by Wenli Zou and coworkers, it was originally released as a part of Molden2aim program (https://github.com/zorkzou/Molden2AIM). The quality of this EDF library is quite good, and is better than the EDF field contained in the .wfx file produced by Gaussian program. This EDF library covers the entire periodic table, up to index of 120. For most elements, it contains both EDF information for large and small core pseudopotentials. Some descriptions about this library posted by its developer can be found in http://bbs.keinsci.com/thread-5354-1-1.html as well as J. Comput. Chem., 39, 1697 (2018). If you do not want Multiwfn to read EDF information from this library automatically, set "isupplyEDF" in settings.ini to 0.
As mentioned in Section 2.5, the .wfx file produced by Gaussian directly carries EDF field when pseudopotential is used. When this kind of file is used as input, Multiwfn by default reads EDF information from EDF field of this .wfx file rather than from the built-in EDF library. If you do not want Multiwfn to read EDF information from this file but from the built-in EDF library, you can change "readEDF" in settings.ini from 1 to 0.
It is noteworthy that Multiwfn also allows reading EDF information from atomic .wfx file produced by Gaussian rather than from the built-in EDF library of Multiwfn (This feature is rarely useful, since as mentioned above, the quality of the built-in EDF library in Multiwfn is better than the EDF library embedded in Gaussian). An example is provided below:
examples\Pt(NH3)2Cl2.wfn is a file corresponding to Pt(NH3)2Cl2, Lanl2 pseudopotential accompanied by Lanl2DZ basis set is used for Pt and Cl, while 6-31G* is used for other atoms. examples\Pt_lanl2.wfx and examples\Cl_lanl2.wfx are the Pt and Cl atomic .wfx files produced by Gaussian 09, in which Lanl2 is also used, therefore their EDF fields represent the inner-core electron density of Pt and Cl replaced by Lanl2.
In order to borrow EDF information from the atomic .wfx files in the analysis of Pt(NH3)2Cl2.wfn, first we need to set "isupplyEDF" parameter in settings.ini to 1. Then boot up Multiwfn and input following commands
examples\Pt(NH3)2Cl2.wfn
Pt // Load EDF information for element Pt
examples\Pt_lanl2.wfx // Take EDF information of Pt from this file
Cl // Load EDF information for element Cl
examples\Cl_lanl2.wfx // Take EDF information of Cl from this file
q // We have finished, exit
Now we can perform wavefunction analysis as usual. But it is better to first carry out some tests to check if inner-core electron density has been properly represented, for example, we integrate electron density over the whole space
100 // 100 Other functions (Part1)
4 // Integrate a function over the whole space
1 // Electron density
The result is 132.00, which is the expected total number of electrons of Pt(NH3)2Cl2. Assume that we did not load the EDF information, then the result will be 52.00, which is just the number of valence electrons of Pt(NH3)2Cl2.
Note that you can also directly input atomic indices instead of element name, for example, inputting 4,8-10,11 means selecting atoms 4,8,9,10,11 in present system. Of course, the atoms you selected each time must correspond to the same element and the same pseudopotential.
It is users' responsibility to prepare the atomic .wfx files. Since there are too many kinds of pseudopotentials and elements, evidently, I am incapable of providing all of them for you.