From mainz@chem.columbia.edu Wed Jul 6 18:11:27 1994 Received: from amazon.chem.columbia.edu for mainz@chem.columbia.edu by www.ccl.net (8.6.9/930601.1506) id QAA05042; Wed, 6 Jul 1994 16:54:43 -0400 Received: by amazon.chem.columbia.edu id AA21440 (5.65c/IDA-1.4.4 for CHEMISTRY@ccl.net); Wed, 6 Jul 1994 16:56:09 -0400 Date: Wed, 6 Jul 1994 16:56:08 -0400 (EDT) From: Daniel Mainz Subject: G92: charge-fitting and polarizabilities To: CHEMISTRY@ccl.net Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Greetings, Gaussian-ophiles. We are attempting to use Gaussian 92 to obtain charges to use in a MD simulation of formaldehyde. We are running Gaussian on an IBM RISC-station. We are having trouble with the population=(chelpg,dipole) option with the 6-311G** basis. For some reason, the chelpg routine thinks that the dipole moment in the z-direction is 13.94D, rather than the 2.77D it should be. Furthermore, chelpg assigns different charges to the two hydrogen atoms of formaldehyde. A similar problem occurs when we use population=(chelpg), again with the 6-311G** basis: the molecule develops a net dipole along the y-axis, in violation of the molecular symmetry. We have noticed that the 6-31G** basis does not suffer from this problem, and gives the expected result. Nevertheless, I would like to use a triple-zeta basis set rather than a double-zeta basis. The same type of problem occurs at the MP2 level of theory, and also using the scf=(tight,direct) keyword. Have others out there seen this behavior, and have quick fixes that we are overlooking? Below are the input file and parts of the output file. Please direct personal replies to bader@chem.columbia.edu. Thank you. Joel Bader and Daniel Mainz, Dept. of Chemistry, Columbia University Input file: --------------------------------------------- #RHF 6-311G** population=(chelpg,dipole) scf=(direct) test formaldehyde experimental geometry 0 1 O C 1 CO H 2 CH 1 AHCO H 2 CH 1 AHCO 3 AD CO 1.203 CH 1.099 AHCO 121.75 AD 180. Relevant parts of the output file: ---------------------------------------------- Dipole moment (Debye): /*from the wave function*/ X= .0000 Y= .0000 Z= -2.7715 Tot= 2.7715 ^ makes sense. .... Breneman (CHELPG) radii used for charge fitting Generate Potential Derived Charges using the Brenneman model, NDens= 1. Grid spacing= .300 Box extension= 2.800 NStep X,Y,Z= 19 25 25 Total possible points= 11875 Number of Points to Fit= 4808 Charge= .00000 Dipole= .0000 -.2127 -13.9414 Tot= 13.9431 1 1 O -1.798223 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2 C .519942 What's going on here? 3 H .615452 4 H .662829