From owner-chemistry@ccl.net Wed Aug 6 09:30:01 2008 From: "errol lewars elewars+*+trentu.ca" To: CCL Subject: CCL: Ab initio on bridged rings Message-Id: <-37496-080805172001-32689-WS5oSwDEm5oVnQ30WBzhUw|server.ccl.net> X-Original-From: errol lewars Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii; format=flowed Date: Tue, 05 Aug 2008 16:25:25 -0400 MIME-Version: 1.0 Sent to CCL by: errol lewars [elewars||trentu.ca] 2008 August 05 Could you give us the structure (cartesians) of one (preferably the smallest) of your troublesome conmpounds)? E. Lewars ============= Simon Halstead shalstead . hit.edu.cn wrote: >Sent to CCL by: "Simon Halstead" [shalstead:hit.edu.cn] > >Dear all, > >I am trying to optimize some bridged (1-4) cyclohexane rings. I initially optimized them using sempiempirical methods. These calculations converged very rapidly. However, I then tried to optimize the resulting structures at a higher level of theory. These high level calculations have failed to converge, despite being run for a large number of steps. I have tried HF, MP2 and B3LYP with a variety of basis sets but nothing appears to converge. Visualizing the outputs of the failed calculations shows no problems with the structure. >Does anyone have any experience with structures like this or can anyone give me a suggestion of how best to optimize bridged rings? >I am using GAMESS if this makes any differnce. > >Thanks for your help, > >Simon Halstead> > > >