Thanks Sir for your response. I am doing all these calculations for oxides. for example I have done the phonon calculations for Cu2O and Ag2O system the details are as follow
Ag2O ecutwfc 70 Ry. Mesh (8x8x8) zone ceneter acoustic mode=1.6 THz (with PBE) Cu2O ecutwfc 95 Ry. Mesh (8x8x8) zone centre acoustic mode = 1.33 THz (PW) I have performed above calculation using tr2_ph=1.0e-14, but the values are almost same. the ecutrho=20times of ecutwfc. Mayank > Dear Mayanka, > > is this a polar material? If so, the violation of the ASR may be justified > by the use of too coarse a k-point mesh. Please, provide more details on the > system and the calculations you are doing. > > SB > > On Jul 1, 2011, at 6:17 AM, mayank gupta wrote: > >> Dear All >> I have a query ragrdin phonon calculations at q=0. When I performed >> the phonon caclualtion at q=0, we didn't get zero enrgy for acoustic >> branches, however they can be set to zero by using acoustic/ crystal >> sum rules. My question is if the zone center acoustic braches values >> are too large (4 THz) even we have implemented very high convergence, >> it is ok to apply ASR. >> >> Thanks >> >> -- >> Mayank BHABHA ATOMIC RESEARCH CENTER MUMBAI, INDIA Office: 022-25595606 Home: 9920397437 / 9869834437