Dear Dr. Hutter,<div> </div><div>Thanks for the reply.</div><div> </div><div>Best, Vishal</div><div> On Tuesday, March 26, 2013 1:30:21 AM UTC-7, jgh wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">Hi the input to the EWALD routines is for historical reasons rather complicated. There are three parameters that define an Ewald calculation: - alpha (width of the Gaussian compensation charge) - the real space cutoff (equal to the cutoff of nonbonded forces in CP2K!) - the reciprocal space cutoff Given a desired accuracy and anyone of the above three parameters determines the possible range of the other two parameters. However, in CP2K you have to define all three parameters independently in the input. In addition, the reciprocal cutoff is given by the number of grid points, this means depends on the box size! And finally, the regression tests are not 'real' inputs. You cannot rely on the parameters used there to give you converged results. You have to find them yourself. regards Juerg Hutter -------------------------------------------------------------- Juerg Hutter Phone : ++41 44 635 4491 Physical Chemistry Institute FAX : ++41 44 635 6838 University of Zurich E-mail: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="lH-Fn8NDo5MJ">hut...@pci.uzh.ch</a> Winterthurerstrasse 190 CH-8057 Zurich, Switzerland --------------------------------------------------------------- -----<a href="javascript:" target="_blank" gdf-obfuscated-mailto="lH-Fn8NDo5MJ">cp...@googlegroups.com</a> wrote: ----- To: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="lH-Fn8NDo5MJ">cp...@googlegroups.com</a> From: vish Sent by: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="lH-Fn8NDo5MJ">cp...@googlegroups.com</a> Date: 03/26/2013 01:17AM Subject: [CP2K:4359] possible bug in Ewald routine ? Dear CP2K users, EWALD section requires one to input ALPHA (ang -1) parameter. In general, I would expect changing this value should not have any affect on the total potential energy of the system. However, when I change ALPHA in the tests files in CP2K tests files, the total potential energy changes a lot (for example water512.inp in tests/Fist folder). I was wondering if there is a bug in ewald routine or I am understanding this wrongly? Any help on this is greatly appreciated. Thanks in advance, Vishal -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="javascript:" target="_blank" gdf-obfuscated-mailto="lH-Fn8NDo5MJ">cp2k+uns...@googlegroups.com</a>. To post to this group, send email to <a href="javascript:" target="_blank" gdf-obfuscated-mailto="lH-Fn8NDo5MJ">cp...@googlegroups.com</a>. Visit this group at <a href="http://groups.google.com/group/cp2k?hl=en" target="_blank">http://groups.google.com/group/cp2k?hl=en</a>. For more options, visit <a href="https://groups.google.com/groups/opt_out" target="_blank">https://groups.google.com/groups/opt_out</a>. </blockquote></div>