<div>Dear QE users,</div><div>I am trying to optimize a single-layer graphene connected to a hydroxyl group.After 48 scf cycles,the optimization result has never reached the convergence value,the force of some atoms is always greater than the convergence threshold.But when I connect an epoxy group instead of a hydroxyl group on the graphene sheet, the optimization can reach convergence after 24 scf cycles.Does anyone know the reason for this?</div><div>Any suggestions would be greatly appreciated.</div><div>Thank you.</div><div><br></div><div> &control</div><div>    calculation  = 'relax',</div><div>    prefix='QJ1GO',</div><div>    pseudo_dir = '/public/home/duan1/GuiWei/pseudo/',</div><div>    outdir='/public/home/duan1/GuiWei/tempdir/'</div><div>    tstress = .true.</div><div>    tprnfor = .true.</div><div>    etot_conv_thr=1.0D-4</div><div>    forc_conv_thr=1.0D-3</div><div>/</div><div> &system    </div><div>    ibrav= 0, </div><div>    nat=66, </div><div>    ntyp=3,</div><div>        </div><div>    occupations='smearing',</div><div>    smearing='mp',</div><div>    degauss=0.02,</div><div><br></div><div>    ecutwfc =40.0</div><div>    ecutrho =320.0</div><div>    </div><div>    vdw_corr='DFT-D'     </div><div>    london_s6 = 0.75</div><div><br></div><div>/</div><div>&electrons</div><div>    conv_thr =  1.0d-8</div><div>    mixing_beta = 0.2</div><div>    mixing_mode = 'local-TF'</div><div>    mixing_ndim=16</div><div>    electron_maxstep=200</div><div>/</div><div>&IONS</div><div>  ion_dynamics='bfgs'</div><div>/</div><div>CELL_PARAMETERS angstrom</div><div>19.680000000000003       0.000000000000010       0.000000000000000</div><div> 0.000000000000000       8.521689973238882       0.000000000000000</div><div> 0.000000000000000       0.000000000000000      25.000000000000000</div><div>ATOMIC_SPECIES</div><div>C  12.0107   C.pbe-rrkjus.UPF</div><div>O   16.00    O.pbe-rrkjus.UPF</div><div>H   1.00     H.pbe-rrkjus.UPF</div><div>ATOMIC_POSITIONS  crystal</div><div>  C   0.0000000000000000   0.0000000000000000   0.2164000000000000</div><div>  C   0.1250000000000000  -0.0000000000000000   0.2164000000000000</div><div>  C   0.0625000000000000   0.2499999999999999   0.2164000000000000</div><div>  C   0.0000000000000000   0.4999999999999999   0.2164000000000000</div><div>  C   0.2500000000000000  -0.0000000000000002   0.2164000000000000</div><div>  C   0.1875000000000000   0.2499999999999999   0.2164000000000000</div><div>  C   0.1250000000000000   0.4999999999999998   0.2164000000000000</div><div>  C   0.0624999999999998   0.7499999999999989   0.2164000000000000</div><div>  C   0.3750000000000000  -0.0000000000000002   0.2164000000000000</div><div>  C   0.3125000000000000   0.2500000000000000   0.2164000000000000</div><div>  C   0.2500000000000000   0.4999999999999999   0.2164000000000000</div><div>  C   0.1875000000000000   0.7499999999999989   0.2164000000000000</div><div>  C   0.5000000000000000  -0.0000000000000002   0.2164000000000000</div><div>  C   0.4375000000000000   0.2500000000000000   0.2164000000000000</div><div>  C   0.3750000000000000   0.4999999999999999   0.2164000000000000</div><div>  C   0.3125000000000000   0.7499999999999988   0.2164000000000000</div><div>  C   0.6250000000000000  -0.0000000000000004   0.2164000000000000</div><div>  C   0.5625000000000000   0.2500000000000000   0.2164000000000000</div><div>  C   0.5000000000000000   0.4999999999999999   0.2164000000000000</div><div>  C   0.4375000000000000   0.7499999999999988   0.2164000000000000</div><div>  C   0.7500000000000000  -0.0000000000000004   0.2164000000000000</div><div>  C   0.6875000000000000   0.2499999999999999   0.2164000000000000</div><div>  C   0.6250000000000000   0.4999999999999999   0.2164000000000000</div><div>  C   0.5625000000000000   0.7499999999999988   0.2164000000000000</div><div>  C   0.8750000000000000  -0.0000000000000004   0.2164000000000000</div><div>  C   0.8125000000000000   0.2499999999999990   0.2164000000000000</div><div>  C   0.7500000000000000   0.4999999999999999   0.2164000000000000</div><div>  C   0.6875000000000000   0.7499999999999989   0.2164000000000000</div><div>  C   0.9375000000000000   0.2499999999999990   0.2164000000000000</div><div>  C   0.8750000000000000   0.5000000000000000   0.2164000000000000</div><div>  C   0.8125000000000000   0.7499999999999988   0.2164000000000000</div><div>  C   0.9375000000000000   0.7499999999999988   0.2164000000000000</div><div>  C   0.0624999725702591   0.0833332967603452   0.2164000000000000</div><div>  C  -0.0000000274297411   0.3333332967603450   0.2164000000000000</div><div>  C   0.1874999725702590   0.0833332967603452   0.2164000000000000</div><div>  C   0.1249999725702590   0.3333332967603450   0.2164000000000000</div><div>  C   0.0624999725702589   0.5833332967603438   0.2164000000000000</div><div>  C  -0.0000000274297409   0.8333332967603447   0.2164000000000000</div><div>  C   0.3124999725702590   0.0833332967603452   0.2164000000000000</div><div>  C   0.2499999725702590   0.3333332967603450   0.2164000000000000</div><div>  C   0.1874999725702590   0.5833332967603448   0.2164000000000000</div><div>  C   0.1249999725702590   0.8333332967603447   0.2164000000000000</div><div>  C   0.4374999725702590   0.0833332967603452   0.2164000000000000</div><div>  C   0.3749999725702590   0.3333332967603450   0.2164000000000000</div><div>  C   0.3124999725702590   0.5833332967603448   0.2164000000000000</div><div>  C   0.2499999725702590   0.8333332967603447   0.2164000000000000</div><div>  C   0.5624999725702590   0.0833332967603451   0.2164000000000000</div><div>  C   0.4999999725702591   0.3333332967603449   0.2164000000000000</div><div>  C   0.4374999725702590   0.5833332967603438   0.2164000000000000</div><div>  C   0.3749999725702590   0.8333332967603447   0.2164000000000000</div><div>  C   0.6874999725702590   0.0833332967603451   0.2164000000000000</div><div>  C   0.6249999725702590   0.3333332967603450   0.2164000000000000</div><div>  C   0.5624999725702590   0.5833332967603447   0.2164000000000000</div><div>  C   0.4999999725702591   0.8333332967603448   0.2164000000000000</div><div>  C   0.8124999725702590   0.0833332967603451   0.2164000000000000</div><div>  C   0.7499999725702590   0.3333332967603450   0.2164000000000000</div><div>  C   0.6874999725702600   0.5833332967603440   0.2164000000000000</div><div>  C   0.6249999725702590   0.8333332967603438   0.2164000000000000</div><div>  C   0.9374999725702590   0.0833332967603450   0.2164000000000000</div><div>  C   0.8749999725702590   0.3333332967603450   0.2164000000000000</div><div>  C   0.8124999725702600   0.5833332967603438   0.2164000000000000</div><div>  C   0.7499999725702590   0.8333332967603438   0.2164000000000000</div><div>  C   0.9374999725702590   0.5833332967603438   0.2164000000000000</div><div>  C   0.8749999725702601   0.8333332967603448   0.2164000000000000</div><div>  O   0.5008325506691220   0.4975899051684459   0.2743438844378600</div><div>  H   0.4505865611121930   0.4983293698599460   0.2875531708238770</div><div>K_POINTS automatic</div><div>2  2  1  0  0  0</div><div><br></div><div><div>Wei gui</div><div>School of Mechanical Engineering，Chongqing University, China</div></div><div><br></div><div><br></div>