good questions... why don't you ask the authors ? stefano luch001 wrote:
> 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 ?CZ^2 /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. I thought to present the formula here. > Unfortunately, I can not add it in my email text. I am very sorry for > that. > > 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. > > Any reply will be appreciated! > > With all my best regards! > > Yours sincerely > > Jingyun Zhang > > > > > > > > > K a p p a \ A N D 1 \ R e e b o k ?? ?? ?? 9 9 ?? > ?? ?? \ ?? ?? \ ?? ?? ?? ?? ?? ?? ?? ?? ?? 1 9 9 ?? ?? ?? , ?? ?? ?? ?? > ?? ! > <http://adtaobao.allyes.com/main/adfclick?db=adtaobao&bid=600,597,58&cid=30015,198,1&sid=32501&show=ignore&url=http://www.taobao.com/vertical/sports/pro.php>
