<div dir="ltr"><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">Dear wien2k users,</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">
We have simulated structural, elcetronic properties and cathode characteristics (in terms of voltage) of a Li based material. When we extract some Li ions from the parent compounds and optimize its volume and lattice parameters, we have obtained a decrements in volume. This decrements has been followed from the concern that Fe+2 ion get oxidized in Fe+3 ions in the delithiated compounds & hence there is an decrements in Fe-O bond length in comparison to the parent (lithiated) one.</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">However, simulation report on the same compound, computed in VASP, has shown that there is actually an expansion of volume after Li extraction. This expansion occurs as when Li ions are taken out from the parent materials there is a decrements of attraction between two layers connected with Li ions previously. At least this is the explanation given by earlier researchers.</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">we optimize the material and its Li extracted counterpart by following the methods:<br>
</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">(1) volume optimization by keeping a:b:c constant, (2) optimizing c/a ratio and (3) optimizing b/a ratio</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">
<br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">we have taken lattice parameters after (3) rd operation (optimization) and calculated DOS and voltage.</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">
<br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">we have also seen....that after 3rd optimization</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px">
(1) there is an increment in b/a ratio in the delithiated part than in the lithiated part in agreement with VASP</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">(2) However, unit cell volume of the de-lithiated part is less than the lithiated compound due to more dominant reduction of Fe-O bond lengths in comparison to the increment of layer-layer separation due to Li ion extractions in our calculation.</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">Now my queries are:</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">
<br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">(1) Is the reduction of Fe-O bond length after Li extraction is more than the decrements of layer-layer separation in FPLAPW calculation?...& that's why we have achieved decrements of volume instead of increments as obtained in VASP?</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">(2) Whether this difference came out from some inherent fact of FPLAPW and PAW (VASP) approach?</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">(3) Whether this is the limitation of the wien2k code itself?</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">(4) Or, whether our methodology of calculation by first volume optimization & then further optimizing c/a and b/a ration....is actually a wrong path...& we should choose some other way for lattice parameter optimization after Li extraction.</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">Sorry for such a long email. However, the answer of these queries are very necessary for our further research and I believe, this discussion will help the community as a whole.</div>
<div style="font-family:arial,sans-serif;font-size:12.727272033691406px"><br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">Thanks in advance,</div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">
<br></div><div style="font-family:arial,sans-serif;font-size:12.727272033691406px">with regards, </div><div><br></div>-- <br>Shamik Chakrabarti<br>Senior Research Fellow<br>Dept. of Physics & Meteorology<br>Material Processing & Solid State Ionics Lab<br>
IIT Kharagpur<br>Kharagpur 721302<br>INDIA
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