Dear developer,
I have vc-relaxed Hf7O8N4 (hafnium oxynitride) assuming the crystal to be rhombohedra with a=b, alpha=beta=90 deg, and gamma=120 deg. So, I used ibrav=4 and gave A,B,C, cosAB, cosAC and cosBC values. Part of the input looks as follows: *&system* * ibrav= 4 * * A=9.4851, B=9.4851, C=8.7867, cosAB=-0.5, cosAC=0.0, cosBC=0.0* * nat=19 , ntyp= 3,* * ecutwfc =70, ecutrho= 840, * * occupations= 'fixed', * * nbnd= 100 * The vc-relax ran successfully and I got the following output: *Final enthalpy = -5322.7186767755 Ry* *Begin final coordinates* * new unit-cell volume = 1536.19292 a.u.^3 ( 227.64030 Ang^3 )* *CELL_PARAMETERS (alat= 17.92424134)* * 0.638651125 0.103631841 -0.047929083* * -0.235833337 0.630643088 -0.049740867* * -0.043220738 -0.085864416 0.635634338* Here, the output cell_parameter values are not consistent with the input. I assumed it as ibrav=4 (hex or rhombohedra), but if I use the output cell_parameter and calculated the final value (using the vector formulas for ibrav=4 from pw.x documentation) for lattice constant ‘a’, I will get different values from different vectors. So, my question is how do we analyse such a system in which we give certain crystal structure as an input and the vc-relax runs successfully (*does not crash*) and give an output which isn’t consistent with the input crystal system? Can I accept the results and carry on further because the vc-relax did not crash meaning that everything is fine? Please help me in this regard. Kind regards, Bharat Thapa PhD student UNSW
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