From jkl@ccl.net Tue Nov 17 18:58:44 1992 From: jkl@ccl.net (Jan Labanowski) Date: Tue, 17 Nov 1992 23:58:44 -0500 Message-Id: <199211180458.AA03173@krakow.ccl.net> To: chemistry@ccl.net Subject: Chemistry Spellchecker The information on SciWords - an English scientific and technical spell checker with 75,000 organic and inorganic chemical names was placed in the CCL archives. To get it, send a message: send spellchecker from chemistry to OSCPOST@ccl.net or OSCPOST@OHSTPY.BITNET. You can also retrieve this advertisement from anonymous ftp on www.ccl.net (file: pub/chemistry/spellchecker). Jan Labanowski jkl@ccl.net From JBITAR@uoft02.utoledo.edu Sun Nov 18 06:24:57 1992 Date: 18 Nov 1992 10:24:57 -0400 (EDT) From: "Joseph E. Bitar" Subject: Population analysis in MOPAC To: chemistry@ccl.net Message-Id: <01GRAKTRTUK20010ID@UOFT02.UTOLEDO.EDU> I am trying to do a population analysis of a triplet species using MOPAC. The keyword MULLIK produces the population anaylsis output, but this matrix is empty (i.e. all values are 0.000000). When I calculate the corresponding singlet, there are reasonable values in the population analysis matrix. 1. Is this due to some incompatability between the keywords MULLIK and UHF or MULLIK and TRIPLET? 2. Is MOPAC simply unable to use a UHF wavefunction to generate the population analysis? 3. If I use G90 or G92 to do my semiempirical calculations (AM1), will I be able to get a population analysis of both the singlet and triplet? Would I use POP=FULL, or is some other combination of keywords necessary? Joseph Bitar Grad. Student Chemistry Dept., Univ. of Toledo From peeter@chem.ut.ee Wed Nov 18 17:08:13 1992 Message-Id: Subject: ZPE and semiempirical methods To: chemistry@ccl.net Date: Wed, 18 Nov 1992 15:08:13 +0200 (EET) From: Peeter Burk Hi, I am Ph D student in Chemistry Department in University of Tartu, Estonia. I recently read in sci.chem some postings about zero point vibrational energies and have a question about them. Namely, is there any need to calculate differences in ZPE-s when I use semiempirical methods such as AM1 or PM3 to study, let's say, keto-enol equillibrium. The idea is that while semiempirical methods are parametrized on the experimental data at 298K, therefore, due to the parametrization procedure the contributions >from the ZPE are already virtually included. Also, at the 298K the differences in vibrational energies may greatly differ from the differences in ZPEs. What's your opinion? Peeter Burk peeter@chem.ut.ee From AHOLDER@VAX1.UMKC.EDU Sun Nov 18 12:51:54 1992 Date: 18 Nov 1992 18:51:54 -0600 (CST) From: Andy Holder Subject: Semiempirical ZPEs To: CHEMISTRY@ccl.net Message-Id: <01GRB2KJROG69S3POM@VAX1.UMKC.EDU> Peeter Burk asked if it was neccessary to compute ZPEs in a semi- empiriccalculation. He then proceede to answer his own question correctly. Since the parameters are derived at 298K, the ZPE is taken up at that point. Note that this is true only at 298K. If one wishes a reference temperature different than this, then perform a thermodynamics calculation and rate it up based on the DH as a function of temperature as given in the heat capacity. On the subject of ZPEs, semiempirical methods do a pretty good job at estimating these for our more restrained ab initio brethren. Andy =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= DR. ANDREW HOLDER Assistant Professor of Computational/Organic Chemistry Department of Chemistry || BITNET Addr: AHOLDER@UMKCVAX1 University of Missouri - Kansas City || Internet Addr: aholder@vax1.umkc.edu Spencer Chemistry, Room 315 || Phone Number: (816) 235-2293 Kansas City, Missouri 64110 || FAX Number: (816) 235-1717 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=