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<DIV><FONT face=Arial size=2>Thank you Paolo and Lorenzo to the replies to my
previous e-mail. I think I didn't explain what I wanted to modify clearly
enough. We modify the explicit exchange to include a descreened
potential:</FONT></DIV>
<DIV><FONT face=Arial size=2>K_x[n]=-0.25 Int[ P[n](r,r')^2 * u(r-r') ] d3r d3r'
</FONT></DIV>
<DIV><FONT face=Arial size=2>where P[n](r,r') is the density matrix of
non-interacting particles and u(r-r') is the descreened interaction (normally
the coulomb interaction u(r)=1/r, but in our case a different
function).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Which files do I need to change for the modified
K_x and its potential? Is it exx.f90 in PW? These explicit exchanges are also
used in Hartree-Fock and B3LYP calculations.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thank you for your help,</FONT></DIV>
<DIV><FONT face=Arial size=2>Helen Eisenberg</FONT></DIV></BODY></HTML>