<div>hi, </div>
<div><strong> When I use ibrav=0 to calculate the force of Si, I encounter some problems. Are there some thing wrong in my codes?</strong></div>
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<div> &system<br> ibrav = 0,<br> nat = 2,<br> ntyp = 1,<br> ecutwfc = 50,<br> A = 5.39780000 ,<br> B = 5.39780000 ,<br> C = 5.39780000 ,<br> cosAB = 0.500000 ,<br> cosAC =
0.500000 ,<br> cosBC = 0.500000 ,<br> /<br> &electrons<br> mixing_beta = 0.7<br> conv_thr = 1.0d-7<br> /<br>ATOMIC_SPECIES<br> Si 28.086 Si.vbc.UPF<br>ATOMIC_POSITIONS crystal<br> Si 0.00000 0.00000 0.00000
<br> Si 0.25000 0.25000 0.25000<br>CELL_PARAMETERS cubic<br> 0.288675135 -0.500000000 0.816496581<br> 0.288675135 0.500000000 0.816496581<br> -0.577350269 0.000000000 0.816496581<br>K_POINTS automatic
<br> 4 4 4 1 1 1 </div>
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<div><strong> The result is below, why does force exit in this situation?</strong></div>
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<div>! total energy = -15.46091639 ryd<br> estimated scf accuracy < 0.00000003 ryd<br> <br> band energy sum = -2.48914635 ryd<br> one-electron contribution = -1.72655466
ryd<br> hartree contribution = 2.24142346 ryd<br> xc contribution = -4.02628209 ryd<br> ewald contribution = -11.94950310 ryd<br> <br> convergence has been achieved<br> <br>
Forces acting on atoms (Ry/au):<br> <br><u> </u><em><strong><u> atom 1 type 1 force = 0.00314138 0.00000000 -0.00856639<br> atom 2 type 1 force = -0.00314138 0.00000000 0.00856639</u>
</strong></em><br> <br> Total force = 0.012904 Total SCF correction = 0.000110<br> <br> <br> entering subroutine stress ...<br> <br> total stress (ryd/bohr**3) (kbar) P= -
86.51<br> -0.00058668 0.00000000 0.00000976 -86.30 0.00 1.44<br> 0.00000000 -0.00058838 0.00000000 0.00 -86.55 0.00<br> 0.00000976 0.00000000 -0.00058914 1.44
0.00 -86.67</div>
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<div><strong>Another question :whether we need not ot set cosAB, cosAC, cosBC when we use ibrav=0?</strong></div>
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<div> thanks.</div>