Hi,<div><br></div><div>The main issue is the mixing algorithm. Change to Broyden.</div><div>Then you could consider the MOLOPT basis sets.</div><div>Also, "c" parameter is a bit small, I would recommend using k-points, al least "1 1 2" grid mesh.</div><div>NGRIDS 12 is less efficient than NGRIDS 5</div><div>Grimme D2 or D3, see the resulting lattice parameters and volume. What's best for your goal?</div><div><br></div><div>What works here:</div><div>...</div><div> &DFT<br> BASIS_SET_FILE_NAME BASIS_MOLOPT<br> POTENTIAL_FILE_NAME POTENTIAL<br> CHARGE 0<br> MULTIPLICITY 1<br> &MGRID<br> CUTOFF 600<br> !REL_CUTOFF 60<br> NGRIDS 5<br> &END MGRID<br> &KPOINTS<br> SCHEME MONKHORST-PACK 1 1 2<br> !SYMMETRY .TRUE.<br> &END KPOINTS<br> &QS<br> METHOD GPW<br> EPS_DEFAULT 1.0E-10<br> &END QS<br> &POISSON<br> PERIODIC XYZ<br> &END<br> &SCF<br> EPS_SCF 1.0E-8<br> SCF_GUESS ATOMIC<br> MAX_SCF 250<br> &MIXING<br> METHOD BROYDEN_MIXING<br> &END MIXING<br> &END SCF<br> &XC<br> &XC_FUNCTIONAL PBE<br> &END XC_FUNCTIONAL<br> &VDW_POTENTIAL<br> POTENTIAL_TYPE PAIR_POTENTIAL<br> &PAIR_POTENTIAL<br> TYPE DFTD2<br> !PARAMETER_FILE_NAME dftd3.dat<br> REFERENCE_FUNCTIONAL PBE<br> R_CUTOFF [angstrom] 15.0<br> !&PRINT_DFTD<br> !&END<br> &END<br> &END VDW_POTENTIAL<br> &END XC<br> &END DFT<br></div><div>...</div><div> &KIND C<br> BASIS_SET DZVP-MOLOPT-GTH<br> POTENTIAL GTH-NLCC-PBE-q4<br> &END KIND<br> &KIND H<br> BASIS_SET DZVP-MOLOPT-GTH<br> POTENTIAL GTH-NLCC-PBE-q1<br> &END KIND<br> &KIND N<br> BASIS_SET DZVP-MOLOPT-GTH<br> POTENTIAL GTH-NLCC-PBE-q5<br> &END KIND<br></div><div>...</div><div><br></div><div>Best,</div><div>Xavier<br><br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Tuesday, August 16, 2022 at 11:39:35 AM UTC-5 shrsi...@gmail.com wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Dear all,<div>I am trying to optimize the crystal structure of carbon nitride (Unit cell contains 144 atoms: C<font size="1">48</font>H<font size="1">24</font>N<font size="1">72</font>). I have tried various suggestions for Basis sets (SZV, DZVP, TZVP), optimization method (CG BFGS, L-BFGS) but cell-optimization is not converging. Energy is highly fluctuating, ultimately forces on a set of atoms become very high and pressure deviation huge. The initial structure is already optimized in FHI-AIMS, and taken from a reference (<a href="https://pubs.acs.org/doi/full/10.1021/acs.chemmater.7b00965" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://pubs.acs.org/doi/full/10.1021/acs.chemmater.7b00965&source=gmail&ust=1660756797171000&usg=AOvVaw06IjbUvg0Bx2kSs-YXMKMF">https://pubs.acs.org/doi/full/10.1021/acs.chemmater.7b00965</a>).</div><div>Particularly, I noticed very high forces on Nitrogen atoms that are involved in Hydrogen-bonding (see attached image of before and after structure)</div><div>I have attached one of the CP2K input file, initial geometry and output file for your reference.</div><div>Thanks in advance.</div><div>Shreya</div><div>Email: <a href data-email-masked rel="nofollow">shrsi...@gmail.com</a></div><div><br></div></blockquote></div>
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