>Dear all,<br>>There are so many pseudopotential files available in www.pwscf.org/pseudo.<br>>And which one is most perfect.For example Al:<br>><span class="grigio"><a class="aranciolink" href="/pseudo/1.3/UPF/Al.pbe-rrkj.UPF">Al.pbe-rrkj.UPF</a>                      </span><span class="grigio"><a class="aranciolink" href="/pseudo/1.3/UPF/Al.pz-vbc.UPF">Al.pz-vbc.UPF</a>              </span><span class="grigio"><a class="aranciolink" href="/pseudo/1.3/UPF/Al.pbe-n-van.UPF">Al.pbe-n-van.UPF</a> </span><span class="grigio"><a class="aranciolink" href="/pseudo/1.3/UPF/Al.pw91-n-van.UPF">>Al.pw91-n-van.UPF</a>        </span><span class="grigio"><a class="aranciolink" href="/pseudo/1.3/UPF/Al.blyp-n-van_ak.UPF">Al.blyp-n-van_ak.UPF</a>             </span><span class="grigio"><a
 class="aranciolink" href="/pseudo/1.3/UPF/Al.bp-n-van_ak.UPF">Al.bp-n-van_ak.UPF</a><br>><br>>The troubleshooting in the manual said that ' maybe your system does have >negative or strange phonon frequencies with the approximations you used '.<br>> <br>>Could anyone tell me which p</span>seudopotential I have to choose if I encountered the >problems.    Thank you so much.<br>>Regurds<br><BR><BR><p>



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