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<DIV><FONT face="Times New Roman">Dear Paolo, thank you for your
answer!</FONT></DIV>
<DIV><FONT face="Times New Roman"></FONT> </DIV>
<DIV>
<DIV><EM>>you mean: "the choice of the q-point grid (i.e. the grid
used<BR>>to calculate the interatomic force constants) does not
depend<BR>>upon the k-point grid (i.e. the grid used to perform
the<BR>>self-consistent calculation")? </EM></DIV>
<DIV><EM></EM> </DIV>
<DIV><FONT face="Times New Roman">Exactly!</FONT></DIV>
<DIV><EM></EM> </DIV>
<DIV><EM>>Correct: the former depends<BR>>upon the range of interatomic
force constants in real space,<BR>>the latter upon the character of the band
structure</EM></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2><FONT face="Times New Roman" size=3>Doesn't the above answer
agree with what I said in the former post? </FONT></FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2><FONT size=3><EM>>I am not sure that the grid used in the
scf calculation<BR>>must be unshifted. What is sure is that the "dense
grid"<BR>>must contain all k-points used in the scf calculation
and<BR>>all the k+q points, where q are the phonon wavevector<BR>>at which
the electron-phonon coefficients are calculated</EM></FONT></FONT></DIV>
<DIV><FONT size=2><FONT size=3><EM></EM></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT face="Times New Roman" size=3>The problem is: if you
choose a shifted k-grid and a unshited </FONT></FONT><FONT size=2><FONT
face="Times New Roman" size=3>q-grid, it seems</FONT></FONT></DIV>
<DIV><FONT size=2><FONT face="Times New Roman" size=3>difficult to maintain the
above restrictions-</FONT></FONT><FONT face="Times New Roman"><FONT size=2><FONT
size=3>namely </FONT></FONT><FONT size=2><FONT size=3>the "the "dense grid"
must</FONT></FONT></FONT></DIV>
<DIV><FONT face="Times New Roman"><FONT size=2><FONT size=3>contain all k-points
used in the </FONT></FONT></FONT><FONT size=2><FONT face="Times New Roman"
size=3>scf calculation and all the k+q points, where q </FONT></FONT></DIV>
<DIV><FONT size=2><FONT face="Times New Roman" size=3>are the
</FONT></FONT><FONT size=2><FONT face="Times New Roman" size=3>phonon wavevector
at which the electron-phonon coefficients</FONT></FONT></DIV>
<DIV><FONT size=2><FONT size=3><FONT face="Times New Roman">are
calculated"</FONT></FONT></FONT></DIV>
<DIV><FONT size=2><FONT size=3><FONT
face="Times New Roman"></FONT></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT size=3><FONT
face="Times New Roman">Best,</FONT></FONT></FONT></DIV>
<DIV><FONT size=2><FONT size=3><FONT
face="Times New Roman"></FONT></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT size=3><FONT face="Times New Roman">Wen YU</FONT></DIV>
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