From chemistry-request@ccl.net Mon Jul 8 20:36:54 1991 Date: Mon, 8 Jul 91 19:10:21 CDT From: shepard@dirac.tcg.anl.gov (Ron Shepard) To: chemistry@ccl.net Subject: Caution is advised -- COLUMBUS 4.1a4 Status: R The COLUMBUS programmers welcome the interest in the COLUMBUS Program System that has been shown by the computational chemistry community. The COLUMBUS Program System is now being tested for public release. This release is expected sometime later this summer, depending on the outcome of the ongoing tests. The current anonymous FTP version of the code is intended for testing purposes only. This version should be considered unreliable for production, research-level calculations. If anyone is interested in experimenting with the code at this level, you are welcome to do so. The COLUMBUS programmers are primarily interested at this time in comments about the installation scripts, and compile-time errors. If you have the capability to compare results with those from other programs, or with older reliable versions of the COLUMBUS codes, then we would also be interested in reports of incorrect results (the simpler the system, the better). The FTP versions of the codes are subject to change at any time, as bugs are corrected in the codes during this testing period. We expect the actual public distribution version of the codes (i.e. the version later this summer) to run correctly, without modification, on several computers, including Alliant, Sun, Cray, Stardent, DEC (VAX and DecStations), IBM (mainframes and workstations), FPS, SGI, Convex, HP, and yes, perhaps even Macintosh PCs. The current installation scripts have been tested on only a few of these machines, and these scripts will be updated between now and the actual release date of the codes to account for any changes required due to these other machines. Since the current codes are for testing purposes only, it is probably better to send comments and suggestions directly to one of the COLUMBUS programmers, instead of cluttering the public bulletin boards with soon-to-be-outdated comments. An announcement will be placed on this bulletin board when the COLUMBUS Program System has passed the testing phase and is generally available. The status of an unknown version can also be determined by examining the file $COLUMBUS/doc/system.history. The system releases with a's and b's in the version number are alpha and beta test versions. The version currently online is 4.1a4, indicating that the code is in an immature and unreliable state. Ron Shepard shepard@tcg.anl.gov From chemistry-request@ccl.net Tue Jul 9 10:31:41 1991 Date: Tue, 9 Jul 91 09:50:23 EDT From: CHAKA%CWGK.DECNET@cwjcc.INS.CWRU.Edu Subject: Calculation of Quadrupole moments with Gaussian 90 To: chemistry@ccl.net Status: R I am using Gaussian90 on the OSC Cray Y-MP to calculate molecular multipole moments. For benzene, using a 6-31G** basis set, the nonzero diagonal elements of the quadrupole tensor are as follows: Qxx -31.2983 Debye-Ang. Qyy -31.2984 Qzz -39.4673 The molecule is in the standard position, i.e. in the xy-plane, centered at the origin, with the C6 axis coincident with the z-axis. I've run a few different basis sets, and the sign and relative magnitudes aren't affected very much. For a charge distribution with the symmetry of a benzene molecule, the quadrupole tensor should be traceless and Qxx = Qyy = -0.5*Qzz. My question is this: How are the quadrupole moments calculated in Guassian, and why are the diagonal elements all the same sign and nearly the same magnitude? I also have a question about the units. Gaussian reports the quadrupole moment in units of Debye-Ang. ( Debye-Ang = 10E-18 esu-cm-Ang = 10E-26 esu-cm-cm.) Experimental results, however, give the benzene quadrupole moment (Qzz) as -33.3E-40 Coulomb-m-m, which is converted to -10.0E-26 esu-cm-cm, in a 1980 paper by J. Vrbancich & G.L.D. Ritchie, J.C.S. Faraday II, 76, 648-649. The results I've been getting from Gaussian for the quadrupole moments are more consistent with C-m-m than Debye-Ang. The dipole moments, on the other hand, agree fairly well (within an order fo magnitude) with experimental results in Debyes. Any light anyone can shed on this would be greatly appreciated. Thanks! ********************************************************************** Anne Chaka (216)-368-3699 Dept. of Chemistry Case Western Reserve University Cleveland, Ohio 44106 chaka%cwgk.decnet@cwjcc.ins.cwru.edu **********************************************************************