<div style="line-height:1.7;color:#000000;font-size:14px;font-family:arial">Dear Alex:<br>I think you can try Berry Phase implemented in the program pw.x.<br>Reference:<br>David Vanderbilt, Berry-phase theory of proper piezoelectric response, J. Phys. Chem. Solids, 61 (2000), 147<br><br><div>--<br>GAO Zhe<br>CMC Lab, Materials Science & Engineering Department,<br>Seoul National University, South Korea<br>        
 </div><div id="divNeteaseMailCard"></div><br>At 2012-08-11 13:47:20,"Alex Mariani" <mariani.alex@rocketmail.com> wrote:<br> <blockquote id="isReplyContent" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><div style="color:; background-color:; font-family:times new roman, new york, times, serif;font-size:12pt"><div><span><br></span></div><div><br></div>  <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;">  <br>
<div id="yiv551715428"><div><div style="color:#000;background-color:#fff;font-family:times new roman, new york, times, serif;font-size:12pt;"><div>Dear all</div><div><span id="yiv551715428result_box" class="yiv551715428" lang="en"><span class="yiv551715428hps">I</span> <span class="yiv551715428hps">want</span> <span class="yiv551715428hps">to calculate</span> <span class="yiv551715428hps">the</span> <span class="yiv551715428hps"></span></span>piezoelectric constant for PbTio3.</div><div><span id="yiv551715428result_box" class="yiv551715428" lang="en"><span class="yiv551715428hps">How</span> <span class="yiv551715428hps">do </span><span class="yiv551715428hps"></span><span class="yiv551715428hps">using</span> the QE <span class="yiv551715428hps">code</span><span>?</span><br> <span class="yiv551715428hps">What is</span> <span class="yiv551715428hps">the</span> <span class="yiv551715428hps">procedure</span><span>?</span><br> <span class="yiv551715428hps">Please</span> <span class="yiv551715428hps">help</span> <span class="yiv551715428hps">me</span><span class="yiv551715428">?</span></span></div><div><br></div><div>best regards</div><div>Alex Mariani</div><div><br></div><div><span class="yiv551715428st">Magadh <i>University</i>
 <br></span></div><div><span class="yiv551715428st">Department of <i>Physics</i></span></div></div></div></div><br><br> </div> </div>  </div></blockquote></div><br><br><span title="neteasefooter"><span id="netease_mail_footer"></span></span>