<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear Swapnil,<div><br></div><div>piezoelectricity is a bulk property. No supercells are needed.</div><div>See e.g.: </div><div>R.M. Martin, PRB 5, 1607 (1972), <span class="Apple-style-span" style="background-color: rgb(255, 255, 255); "><a href="http://link.aps.org/doi/10.1103/PhysRevB.5.1607">http://link.aps.org/doi/10.1103/PhysRevB.5.1607</a></span></div><div>S. de Gironcoli et al., <span class="Apple-style-span" style="line-height: 18px; ">Phys. Rev. Lett. 62, 2853–2856 (1989), </span><span class="Apple-style-span" style="background-color: rgb(255, 255, 255); "><a href="http://link.aps.org/doi/10.1103/PhysRevLett.62.2853">http://link.aps.org/doi/10.1103/PhysRevLett.62.2853</a></span></div><div><span class="Apple-style-span" style="background-color: rgb(255, 255, 255); "><br></span></div><div><span class="Apple-style-span" style="background-color: rgb(255, 255, 255); ">Regards, SB</span></div><div><br></div><div><font class="Apple-style-span" color="#323232" face="arial, helvetica, sans-serif"><span class="Apple-style-span" style="font-size: 12px;">, <br></span></font><div><div>On Oct 11, 2011, at 6:47 PM, swapnil chandratre wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi,<div><br></div><div>I want to understand the concept of piezoelectricity in Espresso, I have some doubts,</div><div><br></div><div>Is it necessary that in order to observe the phenomenon in direct manner (ie application of strain to get polarization), i need to create vaccum in the direction of polarization? or i can work with periordic systems, and observe polarization.?</div>
<div><br></div><div>With respect to the same, if i want to see the effect of field on length dimension of input geometry, I have to proceed with applying vaccum in that direction.? </div><div><br>Is my understanding of the approach incorrect ? can anyone help me understand it better.</div>
<div><div><br></div>-- <br>Regards,<br>Swapnil Chandratre<br>Graduate Student<br>Dept. of Mechanical Engineering,<br>University of Houston,<br>Houston, TX<br>(M)-713-294-9546<br>
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