<div dir="ltr"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">Dear QE users,</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">I am a PhD student working with Berry phase theory of polarization calculations of single layer 2D material hBN in quantum espresso (applying vacuum in the z-direction).</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">I found -0.0000002 C/m^2 polarization from lberry=.true. in QE; however, total phases belonging to electronic and ionic contributions are found as equal to each other and given as 0.40381 and -0.40381 with 5 significant digits.</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">Is it OK to take -0.0000002 C/m^2 as the polarization of the system? or Is this a numerical error?</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">Also, when I change the dimension of the unit cell in z-direction and position of the material inside the cell, this polarization value changes even though I use the same material.</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">Are all those numerical errors or physical phenomena because I know that there are vacuum fluctuations and Lamb modes, and so on? Can we probe those with QE?</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">I look forward to hearing from you soon.</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">Best regards,</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">Aykut Turfanda</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">PhD student at Istanbul Technical University</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">###############################</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"> SUMMARY OF PHASES</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">                               ~~~~~~~~~~~~~~~~~</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">                          Ionic Phase: -0.40381</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">                     Electronic Phase:  0.40381</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">                          TOTAL PHASE: -0.00000 MOD_TOT: 1</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">                             VALUES OF POLARIZATION</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">                             ~~~~~~~~~~~~~~~~~~~~~~</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">        The calculation of phases done along the direction of vector 3</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">        of the reciprocal lattice gives the following contribution to</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">        the polarization vector (in different units, and being Omega</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">        the volume of the unit cell):</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">           P =  -0.0000030  (mod  40.7880378)  (e/Omega).bohr</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">           P =  -0.0000000  (mod   0.0514003)  e/bohr^2</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">           P =  -0.0000002  (mod   2.9386420)  C/m^2</span><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><br style="padding:0px;margin:0px;color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px"><span style="color:rgb(0,0,0);font-family:Menlo,Consolas,"Lucida Console","DejaVu Sans Mono",monospace;font-size:12px">        The polarization direction is:  ( 0.00000 , 0.00000 , 1.00000 )</span><br></div>