A few weeks back we wrote about using WFN(X) files with MultiWFN in order to find σ-holes in halogen atoms by calculating the maximum potential on a given surface. We later found out that using a chk file to generate a wfn(x) file using the guess=(read,only) keyword didn’t retrieve the MP2 wavefunction but rather the HF wavefunction! Luckily we realized this problem very quickly and were able to fix it. We tried to generate the wfn(x) file with the following keywords at the route section
#p guess=(read,only) density=current
but we kept retrieving the HF values, which we noticed by running the corresponding HF calculation and noticing that every value extracted from the WFN file was exactly the same.
So, if you want a WFN(X) file for post processing an MP2 (or any other post-HartreFock calculation for that matter) ask for it from the beginning of your calculation in the same job. I still don’t know how to work around this or but will be happy to report it whenever I do.
PS. A sincere apology to all subscribers for getting a notification to this post when it wasn’t still finished.
perhaps this is usefu informationl:
I don’t think there is an “MP2” wavefunction, it’s a perturbative correction to the Hartree Fock wavefunctions, so you just get an energy correction.
There are variational post HF methods such as CCSD, which should give you a density=current which is distinct to the HF orbitals.
You are absolutely right, thanks for pointing it out!