From owner-chemistry@ccl.net Wed Sep 23 06:44:00 2020 From: "Wendy Anne Warr wendy]*[warr.com" To: CCL Subject: CCL: Free report on ChemAxon meeting Message-Id: <-54175-200923064231-3798-633auaaipBnBAot/a/kbMg#,#server.ccl.net> X-Original-From: "Wendy Anne Warr" Date: Wed, 23 Sep 2020 06:42:29 -0400 Sent to CCL by: "Wendy Anne Warr" [wendy,+,warr.com] My report on the recent virtual ChemAxon user meeting is available on open access at https://chemaxon.com/news/wendy-warrs-report-cheminfo-stories-2020. Interesting meeting and it will cost you nothing to read all about it. My most recent report in the ACS Meeting series is still available for licensing: Chemical Information and Computation 2020, Number One. 259th ACS National Meeting and Miscellaneous Other Meetings, see http://warr.com/morepubs.html and https://www.warr.com/. Wendy Dr. Wendy A. Warr Wendy Warr & Associates 6 Berwick Court, Holmes Chapel Cheshire, CW4 7HZ, England Tel./Fax +44 (0)1477 533837 wendy|-|warr.com http://orcid.org/0000-0002-7064-4739 http://www.warr.com Skype: wendyannewarr Twitter: |-|WendyAnneWarr From owner-chemistry@ccl.net Wed Sep 23 10:12:00 2020 From: "Jens Spanget-Larsen spanget*ruc.dk" To: CCL Subject: CCL: Intramolecular H-bonding and DFT-D Message-Id: <-54176-200923101102-10114-As/FOBGnOJQ9jqxGeD/meg|,|server.ccl.net> X-Original-From: "Jens Spanget-Larsen" Date: Wed, 23 Sep 2020 10:10:59 -0400 Sent to CCL by: "Jens Spanget-Larsen" [spanget,,ruc.dk] Dear CCL, I am looking for information on the performance of DFT-D procedures in the prediction of vibrational wavenumbers for intramolecularly hydrogen-bonded X-H..Y structures. How does the dispersion correction affect the prediction of the X-H stretching wavenumber? Do calculations with the dispersion correction improve correlation with experimental wavenumbers? Yours, Jens >--< From owner-chemistry@ccl.net Wed Sep 23 11:57:00 2020 From: "Stefan Grimme grimme#,#thch.uni-bonn.de" To: CCL Subject: CCL: Intramolecular H-bonding and DFT-D Message-Id: <-54177-200923115458-10018-LJgLj/7dwXr1ZdmbYo8ROw:_:server.ccl.net> X-Original-From: "Stefan Grimme" Date: Wed, 23 Sep 2020 11:54:57 -0400 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 Stefan