From chemistry-request@server.ccl.net Thu Jun 24 02:17:49 1999 Received: from ns.jnj.be (ns.jnj.be [194.74.108.67]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id CAA21331 for ; Thu, 24 Jun 1999 02:17:49 -0400 Received: from ns.jnj.be by ns.jnj.be id IAA06527; Thu, 24 Jun 1999 08:14:14 +0200 (MET DST) Received: FROM ns.jnjeu.jnj.com BY ncsbebesvc06.jnjeu.jnj.com ; Thu Jun 24 08:13:43 1999 Received: from ns.jnj.be by ns.jnj.be id IAA11074; Thu, 24 Jun 1999 08:13:42 +0200 (MET DST) Received: by ncsbebeexh3.ncsbe.jnj.com with Internet Mail Service (5.5.2448.0) id ; Thu, 24 Jun 1999 08:13:41 +0200 Message-ID: <63575A10E3FAD1119DDC0008C7242D3E7BD0B0@JANBEBEEXS3.janbe.jnj.com> From: "Langenaeker, Wilfried [JanBe]" To: "'chemistry@ccl.net'" Subject: electrostatic potential based population analysis techniques Date: Thu, 24 Jun 1999 08:13:39 +0200 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2448.0) Content-Type: text/plain; charset="iso-8859-1" Hi, We are using the electrostatic potential based population analysis techniques on a number of organic systems and encountered a problem with benzene. The symmetry is not present in the charges: we found two types of C-atoms and H-atoms (both in SPARTAN and Gaussian). Increasing the number of points used in the procedure does solve the problem but also increases the cpu-time dramatically. Can anybody explain why this effect is so large (in SPARTAN at the HF/3-21G* level with 1 point per atomic unit the two charges for carbon are -0.163028 and -0.118392) and tell us if it is only a problem in highly symmetrical systems? Does anyone know about a systematic study of this phenomenon? Best regards, Wilfried Langenaeker