From chemistry-request $#at#$ www.ccl.net Fri Jan 8 11:48:12 1999 Received: from mailhost.lanl.gov (mailhost.lanl.gov [128.165.3.12]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id LAA11469 Fri, 8 Jan 1999 11:48:11 -0500 (EST) Received: from [128.165.22.209] (machgs.lanl.gov [128.165.22.209]) by mailhost.lanl.gov (8.9.1a/8.9.1/(cic-5, 7/9/98)) with SMTP id JAA22595 for ; Fri, 8 Jan 1999 09:48:09 -0700 X-Sender: schrecke \\at// t12mail.lanl.gov Message-Id: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Date: Fri, 8 Jan 1999 09:51:11 -0600 To: CHEMISTRY -x- at -x- www.ccl.net (CCL) From: schrecke(+ at +)t12.lanl.gov (Georg Schreckenbach) Subject: Summary: G94/98: How to skip SCF completely? Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by www.ccl.net id LAA11470 Dear CCL, this is the summary for my earlier query on how to use input ("guess") MOs to calculate properties like nmr in G94/98. The essential answer is, it doesn't work (cf. the comments by Mike Frisch -- and he should know ...). Quite a few people suggested the keywords "Guess=(Read,Only)". It is possible to calculate population stuff and related properties with this feature, but it is impossible to go into the CPHF equations (l1002). Further, I'd like to single out the response by Rene Fournier: when posting my question, I was hoping for something along the lines of his suggestion. In this respect, all I found in the code is the old link 503 that seems to do the direct minimazation that Rene suggested. However, it is, apparently, restricted to 256 basis functions (I have a lot more), and I don't really know how to use it anyways. Finally, I wish to pass on the comment by Marta ForÈs i Bocsh : She had posted -- and summarized -- a related question some weeks ago. You can search the CCL archives, or get her summary from me. Thanx to all who took the time to reply! And, please feel free to comment on this further. Best regards, Georg -- Dr. Georg Schreckenbach Tel: (USA)-505-667 7605 Theoretical Chemistry T-12 FAX: (USA)-505-665 3909 M.S. B268, Los Alamos National E-mail: schrecke # - at - # t12.lanl.gov Laboratory, Los Alamos, New Mexico, 87545, USA Internet: http://www.t12.lanl.gov/~schrecke/ ============================ Here are the detailed answers: ============================ Original question: Dear CCL, here is a GAUSSIAN related question: I would like to calculate some properties (like forces or NMR) based solely on the "input guess". How ~is this best done? (Or is it possible at all in GAUSSIAN?) More specifically, I imagine to have some input MOs using the "Guess=Read" command. I would specify a certain DFT method, say, and then go on to calculate the desired properties. What I have tried so far is the following. A) specify a "non-standard route" that resembles a standard route but contains no 500 links. Didn't work because the subsequent links requested some files that had not been written. Perhaps one can do this in a more clever way? B) Specify "SCF(MaxCycle=1)" as well as the appropriate flags to avoid the error termintation due to incomletely converged SCF. These flags are IOp(8/7=1,5/13=1). This procedure comes close to what I want, in particular if I use SCF=QC. However, the one SCF cycle is still too much because it does modify the input MOs as is clearly visible from the output. Hence, I would want to avoid it! Any comments or suggestions? -- I will summarize as usual. Thank you very much! Georg ============================ 1) response by Mike Frisch: From: frisch {*at*} lorentzian.com (Mike Frisch) You could probably hack the program to do this, but all of the properties in Gaussian are based on derivative expressions which are derived assuming that the appropriate SCF equations have been solved. In order to use orbitals and or a density that comes from somewhere else, the CPHF/CPKS equations and possibly other terms would need to be modified to reflect how the density was determined and how it changes in response to the perturbations of interest. Mike ============================ 2) response by Rene Fournier: From: Rene Fournier Hello, In most programs the obvious way would be to use simple mixing convergence procedure with a mixing parameter equal to zero. Can you do that in Gaussian? -------------------------------------------------------------------- | Rene Fournier | Bureau/Office 303 Petrie | | Chemistry Dpt, York University | (416) 736 2100 Ext. 30687 | | 4700 Keele Street, Toronto | FAX: (416) 736-5936 | | Ontario, CANADA M3J 1P3 | e-mail: renef-!at!-yorku.ca | -------------------------------------------------------------------- ============================ 3) One example of a response suggesting Guess=(Read,Only): (Quite a few people proposed the same thing.) From: Darko Babic Dear George, This is what I've found in the G98 manual: "Guess(Only,Read): May also be used to produce population and other post-calculation analyses from the data in a checkpoint file. For example, these options alone will produce a population analysis using the wavefunction in the checkpoint file. Guess(Only,Read) Prop will cause electrostatic properties to be calculated using the wavefunction in the checkpoint file." I hope this helps. If it doesn't, I am afraid that there is no simple way to achieve this. Please, let me know if this happens. Sincerely, Darko Babic Institute "Rudjer Boskovic" HR-10001 Zagreb, P.O.B. 1016 Croatia ============================ 4) Response by Neil Henson: From: Neil Henson What does it do with "SCF(MaxCycle=0)"? [Comment by G.S.: It goes to the default] How about setting the SCF convergence criteria to something ridiculous so that it is already converged before it starts? [Comments by G.S.: a) there is some maximum possible value for the convergence criteria, and it is still to low. b) it should do one cycle anyhow] Neil. -- * Neil Henson Hartlepool Renaissance: a marina, * * neil.henson -x- at -x- lanl.gov/chimera -x- at -x- hubwest.com a hung monkey and much much more * * http://www.t12.lanl.gov/~njh Tel: 505-667-7795 Fax: 505-665-3909 * * Group T-12, Mail Stop B268, Los Alamos National Laboratory, NM 87545, USA *