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<div dir="ltr"><span style="font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Dear all,</span>
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I am trying to calculate the Helmholtz free energy at different temperatures, for the system I am working on, using the THERMO_PW package; however I am getting completely different results using two different calculation schemes:</div>
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<li><span>Using the elastic constants calculation, more specifically the ' what='scf_elastic_constants' ' calculation in thermo_control, I get (already converged):
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# T energy free energy entropy Cv
<div> 0.10000000E+01 0.252357387447E-03 <b> </b>0.251452023143E-03 0.905364304283E-06 0.269932608244E-05</div>
<div> 0.40000000E+01 0.318043336494E-03 0.217216988656E-03 0.252065869595E-04 0.383593024514E-04</div>
<div> 0.70000000E+01 0.453884623458E-03 0.102158461196E-03 0.502465946088E-04 0.497562746839E-04</div>
<div> 0.10000000E+02 0.609349183616E-03 <b>-0.774788213918E-04</b> 0.686828005008E-04 0.533155503573E-04</div>
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Using 'what=scf_dos' with the by default value of 'deltae', and tricking the code by adding a small degauss value to print out the thermal properties (otherwise it would just print the DOS) , I get completely different results (already converged):</li></ol>
<div># T energy free energy entropy Cv chemical pot</div>
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<div> 0.00000000E+00 0.000000000000E+00 0.000000000000E+00 0.000000000000E+00 0.000000000000E+00 0.236129792532-309</div>
<div> 0.10000000E+02 -0.507393714643E+02 <b>-0.507393714856E+02</b> 0.213693218155E-08 0.168706631869E-08 -0.138111664504E+00</div>
<div> 0.20000000E+02 -0.507393714632E+02 -0.507393715059E+02 0.213701188859E-08 0.168699149041E-08 -0.138010404856E+00</div>
<div> 0.30000000E+02 -0.507393714628E+02 -0.507393715269E+02 0.213703845766E-08 0.168696654611E-08 -0.137909145207E+00</div>
<div> 0.40000000E+02 -0.507393714626E+02 -0.507393715481E+02 0.213705174220E-08 0.168695407368E-08 -0.137807885558E+00</div>
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<div><span> 0.50000000E+02 -0.507393714640E+02 -0.507393715709E+02 0.213694949334E-08 0.168705006813E-08 -0.137706592829E+00</span></div>
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So which of these values are to be trusted? I do understand that '2.' is probably for metals (the system I am working on, is a semiconductor), but I did not expect this discrepancy in the results.</div>
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Any information would be appreciated</div>
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Elie Moujaes</div>
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Adjunc professor</div>
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Federal University of Rondonia</div>
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Brazil<br>
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