From owner-chemistry@ccl.net Thu Aug 27 06:42:00 2015 From: "Ramon Crehuet rcsqtc#,#iqac.csic.es" To: CCL Subject: CCL:G: H-bond distance with different solvation models Message-Id: <-51625-150827064015-16586-Smh/hLSx4idhQLvyMrxJhA : server.ccl.net> X-Original-From: Ramon Crehuet Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=utf-8; format=flowed Date: Thu, 27 Aug 2015 12:39:57 +0200 MIME-Version: 1.0 Sent to CCL by: Ramon Crehuet [rcsqtc_+_iqac.csic.es] Dear all, I would like to study the dependence of an H-bond distance with the dielectric constant of water (which depends on temperature, pressure, etc). My system consists of a water molecule and a small molecue containg a donating NH group. I have run the same calculations with Gaussian, using the PCM model and with Orca, using the Cosmo model, obtaining different results. For an epsilon range of 80-95, the Cosmo in Orca changes the H-bond from 1.85A to 1.95A. The same model with Gaussian PCM gives a distance that is constant to 3 significant digits: 1.897A. Gaussian seems to be correctly reading the epsion, as the log file states: Solvent : Water, Eps= 95.000000 Eps(inf)= 1.777849 Being electrostatic in character, I would expect the H-bond distance to depend on the dielectric constant. Beyond that, are there any reasons to prefer one of the methods? Thanks in advance, Ramon -- Ramon Crehuet Cientific Titular (Assistant Professor) Institute of Advanced Chemistry of Catalonia IQAC - CSIC http://www.iqac.csic.es/qteor https://twitter.com/rcrehuet http://ramoncrehuet.wordpress.com/ Tel. +34 934006116 Jordi Girona 18-26 08034 Barcelona (Spain)