From owner-chemistry@ccl.net Sat Apr 18 12:52:01 2015 From: "Safiya Ess Amer amersaf85_-_yahoo.com" To: CCL Subject: CCL: The best molecule specification format Message-Id: <-51266-150418124746-7810-xzEfPCW7MTcM+DUg4CcWCg[*]server.ccl.net> X-Original-From: "Safiya Ess Amer" Date: Sat, 18 Apr 2015 12:47:45 -0400 Sent to CCL by: "Safiya Ess Amer" [amersaf85././.yahoo.com] Hi all I want to do geometry optimization of a system, what is the best molecule specification format, Z-Matrix, Cartesian coordinates, or Mixed to do that? Safiya Amer Grduate Student amersaf85/./yahoo.com From owner-chemistry@ccl.net Sat Apr 18 14:49:01 2015 From: "Grigoriy Zhurko reg_zhurko/a\chemcraftprog.com" To: CCL Subject: CCL: Optimization in Z-matrix vs Cartesian coordinates Message-Id: <-51267-150418144547-9300-NXACPGNVAmxstGhXBYAG3w(0)server.ccl.net> X-Original-From: Grigoriy Zhurko Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Date: Sat, 18 Apr 2015 21:45:42 +0400 MIME-Version: 1.0 Sent to CCL by: Grigoriy Zhurko [reg_zhurko__chemcraftprog.com] Hello, I initially supposed that a geometry optimization, if it is performed in properly composed Z-matrix, takes less optimization steps than if it runs in Cartesian coordinates. Is that wrong? A properly constructed Z-matrix, as far as I suppose, must use dummy atoms for each aromatic cycle in the molecule (the dummy atom is placed in the center of a cycle). I don't mean here the symmetry constraints. I want to compare the speed of geometry optimization of a non-symmetrical molecule (C1) in Z-matrix and Cartesian coordinates. I have this question because I have implemented automatic generation of Z-matrix in my program Chemcraft, and I wonder whether this feature can be useful. I appreciate any suggestions, in which cases such feature can be used. Grigoriy Zhurko.