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<div><span></span>Dear developers,</div><div> I want to ask a trivial question about total local potential Vtot (V_Hartree + Vxc + V_ion), i.e., the variable <b>vrs </b>in electron.f90 (correct me if I am wrong). When we move a specific atom along a specific direction, does the derivative quantity dVtot/dR remain unchanged ?</div><div> I try 0.01~0.1 Angstrom as the amplitude of the displacements, and find that dVtot/dR is not independent of dR. does the differece arise from the numerical error or theoretically <span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">should</span><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;"> </span><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">dVtot/dR depend on dR? If the former is right, then how long is the optimal value of dR for this calculation generally?</span></div><div><br></div><div>Best regards!</div><div><br></div><div>Jiqiang Li</div><blockquote style="margin-top: 0px; margin-bottom: 0px; margin-left: 0.5em;"><div><div class="FoxDiv20150615205930735662"><div class="gmail_extra"><div class="gmail_signature"></div>
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