<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:arial, helvetica, sans-serif;font-size:10pt"><DIV>Hello</DIV>
<DIV>I mean, for example in the case of ALAs (P. Giannozzi et al PRB 43, 7231 (1991)), the LO mode in the Gamma-X direction is very flat (mentioned by the authors, too). </DIV>
<DIV>Is it related to the long interaction caused by the band structure (Sokel & Harrison PRL 36, 61)?</DIV>
<DIV>Sorry about the affiliation</DIV>
<DIV>Thank You</DIV>
<DIV> </DIV>
<DIV>R. Ebraahimi</DIV>
<DIV>Graduate Student- Tehran University</DIV>
<DIV> </DIV></div><br>
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