<div dir="ltr">Hi! I am a beginner in CP2K and I encountered with such problem: when I carried out the test CUTOFF value optimization in single point mode the total energy has significant changes even at large CUTOFF values (350-500 Ry). The REL_CUTOFF value is constant (60 Ry). For test example I chose the small maleimide molecule. I tried to enlarge the cell volume (ABC = 30, 30, 30), but for larger cell I obtained the same picture for TOTAL_E changes. What am I doing wrong? I will be very grateful for your advices. My ultimate goal is to study the mechanisms of organic reactions in a solvent medium by DFT molecular dynamics.<div><div class="prettyprint" style="background-color: rgb(250, 250, 250); border-color: rgb(187, 187, 187); border-style: solid; border-width: 1px; word-wrap: break-word;"><code class="prettyprint"><div class="subprettyprint">CUTOFF (Ry) TOTAL_E 50 -64.842624462853280 150 -66.596463098602229 200 -66.596086697673911 250 -66.593017494126642 300 -66.591148878993607 350 -66.590341443197801 400 -66.590268413708017 450 -66.590267280865888 500 -66.590221265788742</div></code></div><div> </div><div> </div><div> </div><div></div></div><div class="prettyprint" style="background-color: rgb(250, 250, 250); border-color: rgb(187, 187, 187); border-style: solid; border-width: 1px; word-wrap: break-word;"><code class="prettyprint"><div class="subprettyprint">Input File: &GLOBAL PROJECT maleimide-CUT50 RUN_TYPE ENERGY PRINT_LEVEL MEDIUM &END GLOBAL &FORCE_EVAL METHOD Quickstep &SUBSYS &KIND C ELEMENT C BASIS_SET DZVP-GTH-q4 POTENTIAL GTH-BP-q4 &END KIND &KIND N ELEMENT N BASIS_SET DZVP-GTH-q5 POTENTIAL GTH-BP-q5 &END KIND &KIND O ELEMENT O BASIS_SET DZVP-GTH-q6 POTENTIAL GTH-BP-q6 &END KIND &KIND H ELEMENT H BASIS_SET DZVP-GTH-q1 POTENTIAL GTH-BP-q1 &END KIND &CELL A 15.00000000 0.000000000 0.000000000 B 0.000000000 15.00000000 0.000000000 C 0.000000000 0.000000000 15.00000000 &END CELL &COORD C -1.34450 -0.60000 0.00000 C -1.34450 0.75700 0.00000 C -0.02500 -0.91990 0.00000 C -0.02500 1.07680 0.00000 N 0.91900 0.07840 0.00000 O 0.31260 -2.08220 0.00000 O 0.31270 2.23910 0.00000 H -2.23620 -1.24920 0.00000 H -2.23620 1.40620 0.00000 H 1.92530 0.07840 0.00000 &END COORD &END SUBSYS &DFT BASIS_SET_FILE_NAME GTH_BASIS_SETS POTENTIAL_FILE_NAME GTH_POTENTIALS &QS EPS_DEFAULT 1.0E-9 &END QS &MGRID NGRIDS 4 CUTOFF 50 REL_CUTOFF 60 &END MGRID &XC &XC_FUNCTIONAL BP &END XC_FUNCTIONAL &END XC &SCF SCF_GUESS ATOMIC EPS_SCF 1.0E-7 MAX_SCF 1 &DIAGONALIZATION ON ALGORITHM STANDARD &END DIAGONALIZATION &MIXING T METHOD BROYDEN_MIXING ALPHA 0.4 BETA 0.5 NBROYDEN 8 &END MIXING &END SCF &END DFT &PRINT &TOTAL_NUMBERS ON &END TOTAL_NUMBERS &END PRINT &END FORCE_EVAL</div></code></div><div><div> </div></div><div> </div><div>Evgeniy </div></div>