From a29d6a357f32bb9ae39735a2797fcd75f039dde2 Mon Sep 17 00:00:00 2001 From: Alon Grinberg Dana Date: Wed, 2 Sep 2026 22:31:28 +0300 Subject: [PATCH] Correct the G4 harmonic frequency scale factor to 0.9992 The G4 entry added in #1004 carries 0.994, derived as 0.980 * 1.014 where 0.980 was refitted with Truhlar's method over the 15-species standard set. G4 is a composite method that defines its own ZPE scale factor: 0.9854, applied to the B3LYP/6-31G(2df,p) frequencies the method prescribes (Curtiss, Redfern and Raghavachari 2007). Refitting it produces a number that disagrees with the method's own definition. Use the method's factor in the field's units: 0.9854 * 1.014 = 0.9992. This also restores consistency with the neighbouring composite entry. cbs-qb3 stores its own method-defined ZPE factor the same way (0.99 * 1.014), so a refit for G4 alone made the two entries mean different things. Adds source 6 for the G4 paper; no existing source id covered it. Effect: relative to no entry at all, the ZPE shift is 0.02-0.10 kcal/mol. Relative to the 0.994 this replaces, values computed with the old entry are low by 0.0059 * ZPE_harm -- 0.15 kcal/mol for a small species, 0.6+ kcal/mol at ZPE ~ 120 kcal/mol. That correction is closed-form per species, so data already computed against 0.994 is recoverable without a re-run. --- data/freq_scale_factors.yml | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/data/freq_scale_factors.yml b/data/freq_scale_factors.yml index 55b1266f94..f8da6a466a 100644 --- a/data/freq_scale_factors.yml +++ b/data/freq_scale_factors.yml @@ -6,6 +6,7 @@ sources: 3: 'http://comp.chem.umn.edu/freqscale/190107_Database_of_Freq_Scale_Factors_v4.pdf' 4: 'Calculated as described in 10.1021/ct100326h' 5: 'J.A. Montgomery, M.J. Frisch, J. Chem. Phys. 1999, 110, 2822-2827, DOI: 10.1063/1.477924' + 6: 'L.A. Curtiss, P.C. Redfern, K. Raghavachari, J. Chem. Phys. 2007, 126, 084108, DOI: 10.1063/1.2436888' freq_scale_factors: 'hf/sto3g, software: gaussian': @@ -179,9 +180,9 @@ freq_scale_factors: source: 5 note: 'Same as cbs-qb3, added for consistency with Arkane' 'g4, software: gaussian': - factor: 0.994 - source: 4 - note: '0.980 * 1.014, the 0.980 value is the ZPE scale factor of G4, fitted with Truhlar''s method over the 15-species standard set' + factor: 0.9992 + source: 6 + note: '0.9854 * 1.014, the 0.9854 value is the ZPE scale factor of G4' 'ccsd/cc-pvdz, software: molpro': factor: 0.947 source: 2