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Implement CABS Singles correction#3265

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foxtran wants to merge 4 commits into
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foxtran:feature/CABS
Open

Implement CABS Singles correction#3265
foxtran wants to merge 4 commits into
pyscf:masterfrom
foxtran:feature/CABS

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@foxtran

@foxtran foxtran commented Jun 16, 2026

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This patch adds CABS Singles correction according to https://www.molpro.net/manual/doku.php?id=explicitly_correlated_methods#cabs_singles_correction

Tests were verified by comparing values from MRCC & MolPro. See basis setup & numbers in tests.

Refs:

  • JCC 127, 221106 (2007); DOI:10.1063/1.2817618
  • JCP 128, 154103 (2008); DOI:10.1063/1.2889388
  • JCC 45, 1247-1253 (2024); DOI:10.1002/jcc.27325

Related to #3264

@jeanwsr

jeanwsr commented Jun 16, 2026

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Still not close enough to MRCC/Molpro result as a HF job, is it?

@foxtran

foxtran commented Jun 16, 2026

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@jeanwsr, MRCC & MolPro are also not consistent... May be cc-pVDZ basis is not consistent between different programs.

I'll try with other basis sets.

@foxtran

foxtran commented Jun 16, 2026

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Ah... The problem is with core electrons.

@foxtran

foxtran commented Jun 16, 2026

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So, the problems were:

  • improper usage of Density Fitting
  • frozen core approximation(s)
  • UHF / ROHF reference comparison for MolPro

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2 participants