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#1 2024-07-03 14:43:11
Join degenerate Wavefunctions MO
Dear Prof. Tian,
Is there a way in Multiwfn to join two molecular orbitals with "equal" energy values?
In the case of option 19 - -menu 100 -- ("combining fragment wavefunctions"), a new wavefunction is obtained with m orbitals from fragment 1 and n orbitals from fragment 2. However, I am interested in join the coefficients of two orbitals with similar energy into the same orbital.
for example:
Thank you very much
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#2 2024-07-03 23:22:54
Re: Join degenerate Wavefunctions MO
Unfortunately, there is no existing function. If you really need this operation, you can consider to modify and recompile source code of Multiwfn to extend a new function. In which, for example, simplying using CO(imo,:)=CO(jmo,:)+CO(kmo,:) will sum up orbital expansion coefficients (w.r.t PGTFs) of orbitals jmo and kmo as imo. Note that after that usually one also needs to perform normalization for the new orbital.
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#3 2024-07-08 01:20:40
- jxzou
- Member
- Registered: 2023-09-11
- Posts: 6
Re: Join degenerate Wavefunctions MO
You can use the Python API `lin_comb_two_mo` in MOKIT, which performs the linear combinations of two MOs
new_mo1 = 0.5*sqrt2*(mo1 + mo2)
new_mo2 = 0.5*sqrt2*(mo1 - mo2)
Note that the constant 0.5*sqrt2 is needed to ensure that MOs are still normalized (to 1.0). Here is the Python script
from mokit.lib.gaussian import lin_comb_two_mo
lin_comb_two_mo('polyacene.fch', 30, 31)Here the integers 30,31 are the 31th and 32th MOs, respectively. MOKIT can be easily installed using conda, please see https://gitlab.com/jxzou/mokit
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