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<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Dear Wien2k users, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>When we consider Zr (hcp) in a tetragonal or orthorhombic lattice, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>we have to consider the c/a optimization. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Now, we can consider Zr in tetragonal lattice with 1 or more than 1
equivalant point also. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>But both these structures are tetragonal. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Now the difference ENE(Zr, hcp)-ENE(Zr,tetragonal, one equivalent
position) <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>and ENE(Zr,hcp)-ENE(Zr,tetragonal, more than 1 equivalent position )
both would be different (after c/a optimization...) <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Both are the measure of the lattice stability for a tetragonal lattice.
In both the cases I get a smooth variation of energy and c/a % change. But I am
not sure which one to take. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>There should be only one value of lattice stability irrespective of 1
atomic position or more than 1 positions. Am I right here? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>What should be the right approach? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>I envisage the following approach <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>1. c/a optimization. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>2. With the equilibrium lattice parameters, force minimize using mini<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>3. With the equilibrium lattice parameters and equilibrium atomic
positions, get the energy vs c/a. plot<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Is the approach right? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><st1:GivenName w:st="on"><font size=2 face="Times New Roman"><span
style='font-size:11.0pt'>Suddhasattwa</span></font></st1:GivenName><font
size=2><span style='font-size:11.0pt'> <st1:Sn w:st="on">Ghosh</st1:Sn><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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