From owner-chemistry@ccl.net Fri Sep 25 12:14:00 2020
From: "Jens Spanget-Larsen spanget__ruc.dk" <owner-chemistry^server.ccl.net>
To: CCL
Subject: CCL: SV: Intramolecular H-bonding and DFT-D
Message-Id: <-54178-200925121231-7497-eFNcstYRmfpuOYgahVEmUA^server.ccl.net>
X-Original-From: Jens Spanget-Larsen <spanget##ruc.dk>
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Date: Fri, 25 Sep 2020 16:12:22 +0000
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Sent to CCL by: Jens Spanget-Larsen [spanget(_)ruc.dk]

Dear Stefan,
thank you for your overview!
Yours, Jens >--<
________________________________________
Fra: owner-chemistry+spanget==ruc.dk##ccl.net [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