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Dear all, <br>
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I am trying to calculate the Helmholtz free energy at different temperatures of a metallic structure (MX2) using the thermo_pw code with what='scf_dos'. I am keeping the default value of "deltae" (as instructed) and using a 10K step for temperature. I am
getting the following values: (values are in Ry/cell as given in the output).<br>
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# T energy free energy entropy Cv chemical pot
<div> 0.00000000E+00 0.000000000000E+00 0.000000000000E+00 0.000000000000E+00 0.000000000000E+00 0.235589973268-309</div>
<div> 0.10000000E+02 -0.821784411055E+02 -0.821784546975E+02 0.135920658754E-05 0.191338052708E-05 0.585081141513E-01</div>
<div> 0.20000000E+02 -0.821784411050E+02 -0.821784682892E+02 0.135920669618E-05 0.191338051035E-05 0.583642780107E-01</div>
<div> 0.30000000E+02 -0.821784411044E+02 -0.821784818806E+02 0.135920685096E-05 0.191338048653E-05 0.582204418969E-01</div>
<div> 0.40000000E+02 -0.821784411048E+02 -0.821784954731E+02 0.135920675050E-05 0.191338050199E-05 0.580766057297E-01</div>
<span> 0.50000000E+02 -0.821784411051E+02 -0.821785090654E+02 0.135920669024E-05 0.191338051157E-05 0.579327695624E-01</span></div>
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<span>While computing the formation energy according to :</span></div>
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<span>Ef=E(Mx2)- E(M)-2*E(X), where E(M) and E(X) are energies per atom of the isolated bulk M and X species. Adding the above values at different T for MX2 and the individual species M and X (that I have not shown here), gives values of Ef such as -40Ry, which
I think are both very large and nonsensical.</span></div>
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<li><span>Are the values of the free energy shown above reasonable?</span></li><li><span>When inserting the temperature-dependent contributions to the formation energy, does one include the electronic contributions or just the vibrational contributions. Most papers discard the electronic part.</span></li></ol>
<div>Any help on this topic is highly appreciated.</div>
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<div>Obs: I am calculating the temperature-dependent parts because Ef at T=0K for the structure I have turned out to be positive.</div>
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<div>Regards</div>
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<div>Elie Moujaes</div>
<div>Adjunct professor level III</div>
<div>Federal University of Rondonia</div>
<div>Porto Velho</div>
<div>Brazil<br>
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