Dear all,
I have read the paper titled ??Theory of systematic absence of NaCl-type
(??-Sn-type) high pressure phases in covalent (ionic) semiconductors?? (Phys
Rev Lett. 82, 767, 1999). The phonon behaviors are dominated by the competition
between the attractive electrostatic Madelung energy ?CZ2/R (where Z is the
excess charge within the atomic sphere) and the repulsive short-range energy. I
can not understand well the formula of the force constant given in the last
part of page 769, which reads:
?????? = nA??????/Rn+2-Z2??????/R3-??R??R??/ R5
How does it come from? Does it apply to all the systems or just apply to some
specific system? The values of A and ?? are determined by what factors?
The authors claimed that the transverse acoustic mode at X point lowers the
repulsive energy and raises the Madelung energy, but why?
I have pondered hardly and consulted with others. But I have reached no
conclusion. I wrote letter to Alex Zunger, one of the two authors. He did not
write back yet.
Any reply will be appreciated!
With all my best regards!
Yours sincerely
Jingyun Zhang
-------------- next part --------------
An HTML attachment was scrubbed...
URL: /pipermail/attachments/20061123/c9c403ed/attachment.htm
