i am using quantum espresso static calculation obeys thermdyanamic stability transition from B1 to B2 transition at 138 gpa so ihave used 24 24 24 kpoint grid for phonon in B2 phase is calculated 4 4 4 grid by linear response calculation but why the instability (negative frequency in phonon ) upto 450 gpa i have used pbe psudo potentials also the lattice constant is exact for experimental data<div>
can metastability have negative frequency so why this occures </div><div>optimisation is ok </div><div>other problem why free energy is not coming for unstable phase for qha code in quantum espresso<br>replay immidiate if u have solution<br>
<div class="gmail_quote">On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo <span dir="ltr"><<a href="mailto:bdslipun@gmail.com">bdslipun@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
sir<div>i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase but the unstability persists upto 500 gpa</div><div>but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24</div><div>what may be reseon i donot know </div>
<div>please help me </div>
</blockquote></div><br></div>