<DIV>Dear Stefano&nbsp;Baroni&nbsp;and Lorenzo Paulatto,</DIV>
<DIV><BR><BR>&gt;Message:&nbsp;3<BR>&gt;Date:&nbsp;Mon,&nbsp;&nbsp;7&nbsp;Dec&nbsp;2009&nbsp;11:09:23&nbsp;+0100<BR>&gt;From:&nbsp;Lorenzo&nbsp;Paulatto&nbsp;&lt;paulatto@sissa.it&gt;<BR>&gt;Subject:&nbsp;Re:&nbsp;[Pw_forum]&nbsp;forces_bp_efield.f90<BR>&gt;To:&nbsp;pw_forum@pwscf.org<BR>&gt;Message-ID:&nbsp;&lt;20091207110923.1a5hjymg0ggk4owc@webmail.sissa.it&gt;<BR>&gt;Content-Type:&nbsp;text/plain;        charset=ISO-8859-1;        DelSp="Yes";<BR>&gt;        format="flowed"<BR>&gt;<BR>&gt;Dear&nbsp;Q.J.&nbsp;Wang,<BR>&gt;what&nbsp;Stefano&nbsp;Baroni&nbsp;says&nbsp;is&nbsp;correct:&nbsp;applying&nbsp;an&nbsp;electric&nbsp;field&nbsp;via&nbsp;&nbsp;<BR>&gt;Berry&nbsp;phase&nbsp;(lefield=.true.)&nbsp;does&nbsp;not&nbsp;work&nbsp;for&nbsp;metals.&nbsp;The&nbsp;code&nbsp;does&nbsp;&nbsp;<BR>&gt;no&nbsp;issue&nbsp;an&nbsp;error&nbsp;because&nbsp;you&nbsp;may&nbsp;still&nbsp;know&nbsp;what&nbsp;you&nbsp;are&nbsp;doing,&nbsp;e.g.&nbsp;&nbsp;<BR>&gt;using&nbsp;the&nbsp;smearing&nbsp;in&nbsp;an&nbsp;insulator.&nbsp;Or&nbsp;having&nbsp;an&nbsp;odd&nbsp;number&nbsp;of&nbsp;&nbsp;<BR>&gt;electrons&nbsp;in&nbsp;an&nbsp;isolated&nbsp;molecule.<BR>&gt;<BR>&gt;In&nbsp;a&nbsp;metal&nbsp;a&nbsp;constant&nbsp;external&nbsp;field&nbsp;only&nbsp;have&nbsp;an&nbsp;effect&nbsp;on&nbsp;the&nbsp;&nbsp;<BR>&gt;surface,&nbsp;usually&nbsp;limited&nbsp;to&nbsp;2-3&nbsp;layers&nbsp;of&nbsp;atoms.</DIV>
<DIV>The system I study is not insulator ,it is semiconductor(doped ZnO)and the system has odd electrons .This can not apply an electic field via Berry phase ?</DIV>
<DIV>--<BR>
<DIV>
<DIV>Best regards</DIV>
<DIV>&nbsp;</DIV>
<DIV>Q.J.Wang</DIV>
<DIV>&nbsp;</DIV>
<DIV>XiangTan University </DIV><BR></DIV></DIV><br><br><span title="neteasefooter"/><hr/>
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