Thank you for your detailed and professional response. I understand now! This computational result was obtained when I was investigating the performance of different k-point calculation settings. <div>In principle, the gamma point calculation setting is reasonable for this system.</div><div> </div><div>best wishes,</div><div>Dongfei </div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Monday, 19 May 2025 at 22:53:17 UTC+8 Jürg Hutter wrote: </div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi These are the total forces for 64 waters from the ripples. (BTW no k-points here, but why do you have a 3 3 1 grid?) GPW PBE 0.011 GPW LDA 0.002 GAPW PBE 0.002 GAPW LDA 0.0001 Keep in mind that these forces are correct forces for the energy functional defined in CP2K. regards JH ________________________________________ From: <a href data-email-masked rel="nofollow">cp...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">cp...@googlegroups.com</a>> on behalf of liu dongfei <<a href data-email-masked rel="nofollow">liud...@gmail.com</a>> Sent: Monday, May 19, 2025 4:28 PM To: cp2k Subject: Re: [CP2K:21478] The total force calculated by CP2K is not zero Thanks for your reply! The attached file is the result of a calculation, showing that the total force of the system is : ------------------------------------------------------- .... 189 2 H -0.02270940 -0.01715719 -0.01124088 190 2 H -0.00819690 0.01778486 -0.00220956 191 2 H -0.00491958 -0.00982567 0.00540266 192 2 H -0.00744376 0.00269638 -0.00803075 SUM OF ATOMIC FORCES 0.00405273 -0.00782982 0.01173920 0.01468126 ------------------------------------------------------- The total force here is not particularly small, and it is comparable to the forces experienced by some H atoms. Is this result reasonable, even considering the ripple effect? best wishes, Dongfei On Monday, 19 May 2025 at 21:26:00 UTC+8 Jürg Hutter wrote: Hi inaccurate numerics can be a source for forces not summing up to zero. However, I assume (we don't know actually, as you don't share the forces) that the residual force is due to the 'ripple effect'. CP2K uses aequidistant grids to calculate XC energies. For such grids there is no longer any translational invariance. regards JH ________________________________________ From: <a href data-email-masked rel="nofollow">cp...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">cp...@googlegroups.com</a>> on behalf of liu dongfei <<a href data-email-masked rel="nofollow">liud...@gmail.com</a>> Sent: Monday, May 19, 2025 5:00 AM To: cp2k Subject: [CP2K:21474] The total force calculated by CP2K is not zero Hi all, I’m currently simulating a pure water system with CP2K. Despite configuring appropriate convergence criteria (e.g., CUTOFF, REL_CUTOFF, and EPS_SCF), the total forces from the calculation do not converge to zero. Attached is my input configuration. Could anyone provide insights into potential causes or recommend literature discussing this specific issue? Thanks in advance! -- You received this message because you are subscribed to the Google Groups "cp2k" group. 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