From laidig[ AT ]pg.com Thu Dec 8 17:18:20 1994 Received: from oldspice.pg.com for laidig-: at :-pg.com by www.ccl.net (8.6.9/930601.1506) id RAA17949; Thu, 8 Dec 1994 17:12:44 -0500 Received: by oldspice.pg.com (8.6.9/8.6.9) id RAA23627; Thu, 8 Dec 1994 17:07:34 -0500 id RAA23627; Thu, 8 Dec 1994 17:07:34 -0500 Received: from pandora.pg.com(137.176.2.4) by oldspice.pg.com via smap (V1.3) id sma023621; Thu Dec 8 22:07:15 1994 Received: from morpheus.pg.com by pandora via SMTP (940715.SGI.52/930416.SGI.AUTO) for "-at-" oldspice.pg.com:JAMES "-at-" unca.edu id AA09430; Thu, 8 Dec 94 17:15:10 -0500 Received: by morpheus (931110.SGI/930416.SGI.AUTO) for ":at:" pandora.pg.com:chemistry ":at:" ccl.net id AA15817; Thu, 8 Dec 94 17:15:10 -0500 Date: Thu, 8 Dec 94 17:15:10 -0500 From: laidig /at\pg.com (Bill Laidig) Message-Id: <9412081715.ZM15815*- at -*morpheus.pg.com> In-Reply-To: "Charles G. James" "CCL:Z matrix to cartesian coord. Question" (Dec 8, 2:27pm) References: <01HKEIFDUL9E051479 -8 at 8- uncavx.unca.edu> X-Mailer: Z-Mail (3.1.0 22feb94 MediaMail) To: "Charles G. James" , chemistry ":at:" ccl.net Subject: Re: CCL:Z matrix to cartesian coord. Question Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 On Dec 8, 2:27pm, Charles G. James wrote: > Subject: CCL:Z matrix to cartesian coord. Question > I do not mean this as an attack upon anyone or anything. However this relates > to information I have to pass on to undergraduates in reference to > computational chemistry. Just this week someone on this mailing list asked for > a way to get 10-15 (significant?) digits, after the komma(decimal), Cartesian > coordinates for a Ih symmetry molecule from the z matrix of a Gaussian > 92 program. Are we at the stage where that many significant digits are given by > any computational chemistry method? Are we at the stage where that many > significant digits are obtainable by any physical method used to measure > structure? I am still warning undergraduates to beware of the number of digits > which can appear in calculations not connected to their measurements or their > original input. Can I now say there are ways out there to get precision only > formerly dreamed by spectroscopist? Are there ways to get structural parameters > to this precision? > > Charles G. James, Jr. Assoc. Professor of Chemistry > Dept. of Chemistry, University of North Carolina at Asheville > Asheville, NC 28804-3299, USA Phone: (704)251-6443 > FAX: (704)251-6041 E-mail: james(+ at +)unca.edu Prof. James, I believe you misunderstood the intent of the message you referred to. The author wanted his high symmetry geometry to be converted from internal to cartesian coordinates to 10-15 digit accuracy. The reason for this is not that the structures are assumed to be good to this many decimal places, but that programs that figure out symmetry from cartesian coordinates very often need the symmetry exactly or nearly exactly before there are able to pick it up. My interpretation is the standard 6 decimal places he has from his g92 output file is not accurate enough for the program he is subsequently using for it determine or to verify that the molecule really is Ih symmetry. Bill -- ****************************************************************************** * "Like jewels in a crown, the precious stones glittered in the queen's * * round metal hat." - Jack Handey * * * * Bill Laidig * * The Procter & Gamble Co. tel 513-627-2857 fax - 1233 * * Miami Valley Laboratories laidig -x- at -x- pg.com (preferred) * * P.O. Box 538707 laidigwd*- at -*pg.com * * Cincinnati, OH 45253-8707 laidig&$at$&qtp.ufl.edu * ******************************************************************************