<div>Hello, everyone. As a benchmark test, I performed the vc-relax+vdW-DF calculations for graphite. The opitimized lattice constants seem to be unreasonable using vc-relax+vdW-DF. It is overestimated about about 29% for a. <span id="tran_0_0">I </span><span id="tran_0_1">don't </span><span id="tran_0_2">know what </span>the <span id="tran_0_3">problem </span><span id="tran_0_4">is.</span></div>

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<div>#############################################################################################<br>          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.01<br>  -0.00000002   0.00000000   0.00000000          0.00      0.00      0.00<br>
   0.00000000  -0.00000002   0.00000000          0.00      0.00      0.00<br>   0.00000000   0.00000000  -0.00000007          0.00      0.00     -0.01</div>
<div><br>     The maximum number of steps has been reached.</div>
<div>     End of BFGS Geometry Optimization<br>Begin final coordinates<br>     new unit-cell volume =    450.28054 a.u.^3 (    66.72469 Ang^3 )</div>
<div>CELL_PARAMETERS (alat=  4.68000000)<br>   1.292794235  -0.000000090   0.000000000<br>  -0.646397196   1.119592604   0.000000000<br>   0.000000000   0.000000000   3.034982637</div>
<div>ATOMIC_POSITIONS (crystal)<br>C       -0.000001693   0.000001693   0.250000000<br>C        0.000001693  -0.000001693   0.750000000<br>C        0.333331648   0.666668352   0.250000000<br>C        0.666668352   0.333331648   0.750000000<br>
End final coordinates<br>######################################################################################</div>
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<div> </div>
<div>&control<br>   calculation = 'vc-relax'<br>!   restart_mode='from_scratch',<br>   prefix='graphite',<br>   tstress = .true.<br>   tprnfor = .true.<br>    pseudo_dir   = "/home/wangvei/works/quantum-espresso/pseudo",<br>
    outdir       = "./",<br>    disk_io  = 'none'<br>    forc_conv_thr = 1.0e-3<br>   nstep =  45  ,<br>               etot_conv_thr = 1.0E-4 ,<br>               forc_conv_thr = 1.0D-3 ,<br>                      iprint = 1 ,<br>
                 max_seconds = 36000 ,<br>                          dt = 100 ,<br>/<br>&system<br>    ibrav           = 4<br>    celldm(1)       = 4.68<br>    celldm(3)       = 2.70<br>    nat             = 4<br>    ntyp            = 1<br>
    occupations = "smearing",<br>    smearing    = "gaussian",<br>    degauss     = 0.002D0,<br>    ecutwfc         = 40.0<br>    ecutrho         = 200<br>    input_dft       = 'vdw1'<br>/<br>&electrons<br>
    conv_thr        = 1.0d-8<br>/<br>&ions<br>/<br>&cell<br>    press_conv_thr  = 0.0D0<br>    press           = 0.D0<br>    cell_dynamics   = 'bfgs'<br>!    cell_dofree     = 'z'<br>/<br>ATOMIC_SPECIES<br>
C   12.00   C.pbe-paw_kj.UPF<br>ATOMIC_POSITIONS {crystal}<br> C     0.00000   0.00000   0.25000<br> C     0.00000   0.00000   0.75000<br> C     0.33333   0.66667   0.25000<br> C     0.66667   0.33333   0.75000<br>K_POINTS automatic<br>
9 9 4 0 0 0<br></div></span>