CCL: SV: Intramolecular H-bonding and DFT-D

 Sent to CCL by: Jens Spanget-Larsen [spanget(_)ruc.dk]
 Dear Stefan,
 thank you for your overview!
 Yours, Jens >--<
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 [owner-chemistry+spanget==ruc.dk##ccl.net] p&#229; vegne af Stefan Grimme
 grimme#,#thch.uni-bonn.de [owner-chemistry##ccl.net]
 Sendt: 23. september 2020 17:54
 Til: Jens Spanget-Larsen
 Emne: CCL: Intramolecular H-bonding and DFT-D
 Sent to CCL by: "Stefan  Grimme" [grimme(-)thch.uni-bonn.de]
 Dear Jens,
 I'm not aware of a benchmark study to this specific question but
 please allow me to give a general answer.
 Dispersion corrections very generally improve the PES for inherently
 overrepulsive (dispersion devoid) functionals giving better energies,
 structures and frequencies. There is no physical reason why the intramolecular
 situation is different from the intermolecular one.
 However, functionals which at intermediate distances
 account for some "dispersion type" correlation like e.g. PBE or LDA
 systematically yield too strong hydrogen bonds and consequently
 too large vibrational red shifts (partially due to artificial CT). In such
 cases adding the "-D" in whatever form would further (wrongly)
 strengthen
 the bonding.
 For proper choices like BLYP, TPSS, B3LYP or similar I don't
 expect any problem.
 Best
 Stefanhttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp-:-//www.ccl.net/chemistry/sub_unsub.shtmlhttp-:-//www.ccl.net/spammers.txt