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Dear Developer(s),</div>
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I have encountered what would appear to be a serious bug in your code. I have been trying to tabulate some elastic constants for Si and Cu only to realize that your code has some issues with some components of the elastic tensor.</div>
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Namely, the c44 component of Si and c11 component of Cu. All my other parameters are within a reasonable range of existing VASP calculations.</div>
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For example Si (in GPa):<br>
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Component<br>
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Materials Project (VASP)<br>
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ESPRESSO with the same routine as Materials Project (I did these calcs)<br>
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c11<br>
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144<br>
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156<br>
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c12<br>
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53<br>
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62<br>
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c44<br>
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75<br>
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104<br>
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I have converged my cutoff parameters and kpoint mesh. I also tried fiddling with the tolerances on energy and forces.<i><b> All of these are converged in the values I show you above</b></i><span style="font-size: 14pt; line-height: normal;">.</span><span style="font-size: 12pt; line-height: normal;">
It would seem both your energies and forces are miscalculated in certain deformation directions (and no I did not apply too much of a deformation). I am fairly certain that these issues have nothing to do with my code as I also implemented it for CP2k and
the results were within acceptable margins of existing code.</span><span style="font-size: 14pt; line-height: normal;"><br>
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<span style="font-size: 12pt; line-height: normal;">If you require any more information to assist you in this effort, let me know.
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