<div dir="ltr">I did some other test with the "GRID" approach above outlined, and I cannot understand where I'm wrong.<div>I tried different libraries during the compilation process, but while the "normal" phonon calculations runs smoothly (but slower, about 1 hour), the "GRID" approach always gave me bad (negative) frequencies (but much faster, about 10 minutes). I'm using ecut=60 and erho=480</div><div><br><div>The phonon results from without using the "-ni 8" approach is:</div><div><div> freq ( 1) = -0.219517 [THz] = -7.322283 [cm-1]</div><div> freq ( 2) = 0.237288 [THz] = 7.915064 [cm-1]</div><div> freq ( 3) = 0.412515 [THz] = 13.760017 [cm-1]</div><div> freq ( 4) = 0.888921 [THz] = 29.651216 [cm-1]</div><div> freq ( 5) = 1.818322 [THz] = 60.652688 [cm-1]</div><div> freq ( 6) = 3.267016 [THz] = 108.975924 [cm-1]</div><div> freq ( 7) = 3.944444 [THz] = 131.572497 [cm-1]</div><div> freq ( 8) = 13.702502 [THz] = 457.066270 [cm-1]</div><div> freq ( 9) = 15.986666 [THz] = 533.257782 [cm-1]</div><div> freq ( 10) = 21.306349 [THz] = 710.703307 [cm-1]</div><div> freq ( 11) = 29.251729 [THz] = 975.732641 [cm-1]</div><div> freq ( 12) = 31.330252 [THz] = 1045.064724 [cm-1]</div><div> freq ( 13) = 40.094614 [THz] = 1337.412380 [cm-1]</div><div> freq ( 14) = 91.247143 [THz] = 3043.677078 [cm-1]</div><div> freq ( 15) = 94.196285 [THz] = 3142.049865 [cm-1]</div></div><div><br></div><div>If I use the "-ni 8" (GRID) I got:</div><div><div> freq ( 1) = -14.549865 [THz] = -485.331266 [cm-1]</div><div> freq ( 2) = -10.853880 [THz] = -362.046453 [cm-1]</div><div> freq ( 3) = -9.921965 [THz] = -330.961126 [cm-1]</div><div> freq ( 4) = -9.680609 [THz] = -322.910351 [cm-1]</div><div> freq ( 5) = -9.593462 [THz] = -320.003431 [cm-1]</div><div> freq ( 6) = -9.461406 [THz] = -315.598531 [cm-1]</div><div> freq ( 7) = -8.724432 [THz] = -291.015732 [cm-1]</div><div> freq ( 8) = -4.051543 [THz] = -135.144927 [cm-1]</div><div> freq ( 9) = 8.067478 [THz] = 269.102094 [cm-1]</div><div> freq ( 10) = 19.972800 [THz] = 666.220885 [cm-1]</div><div> freq ( 11) = 29.137064 [THz] = 971.907843 [cm-1]</div><div> freq ( 12) = 30.784477 [THz] = 1026.859612 [cm-1]</div><div> freq ( 13) = 39.868296 [THz] = 1329.863222 [cm-1]</div><div> freq ( 14) = 91.702737 [THz] = 3058.874040 [cm-1]</div><div> freq ( 15) = 94.287387 [THz] = 3145.088688 [cm-1]</div></div><div><br></div><div>A lot of negative frequencies appear and sometimes (with a bigger system) I got a ************ in the matdyn file (in this case an error is printed).</div><div>Any idea?</div><div>Anybody else had this kind of problem?</div><div>Thank you,</div><div><br></div><div> Carlo</div></div><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_extra"><div><div class="h5"><br></div></div></div></blockquote></div>-- <br><div class="gmail_signature"><div dir="ltr"><pre>------------------------------------------------------------
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