 energy in Hartree. It should be set to the lowest value possible in theory. However, in practice, a too low value of eta would induce huge and unstable GW corrections. The default value is usually very accurate and there is no need to use a lower value. But for states apart from the band gap, a large value of eta may be beneficial for stability. eta=0.01 is already much more stable. Note that for QSGW increasing eta is most often unavoidable.</li><br>
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