<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Cambria;
panose-1:2 4 5 3 5 4 6 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Cambria","serif";
color:black;
font-weight:normal;
font-style:normal;
text-decoration:none none;}
.MsoChpDefault
{mso-style-type:export-only;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-GB" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black">Dear developers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black">I study flexoelectric effect which can be seen as a repulsion of TA and TO branches in the vicinity of gamma point. I calculate phonon dispersion of cubic SrTiO3.
It’s essential for me to have adequate picture of phonons in the vicinity of gamma point (at least for q>0.05).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black">The picture shows TA and TO branches single q-point (st.ph.single.in) calculations (grey dots) and dispersion (st.ph.disp.in) for 8x8x8 mesh.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB"><img width="481" height="735" id="Picture_x0020_2" src="cid:image003.png@01CFBBD0.39A26750"></span><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black">With used parameters ph.x fails to give right values for small values of q-vector. I guess it’s due to numerical errors of the code.<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black">What are the main reasons for this numerical error when we go close to gamma point. Which parameters should I adjust to improve the situation?<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black">Attached, all relevant inputs and outputs<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria","serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">Sincerely yours,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">Alexander Kvasov<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">Ceramics Laboratory /
</span> <span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">THEOS (Theory and Simulation of Materials) Laboratory<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="FR-CH" style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">École Polytechnique Fédérale de Lausanne (EPFL)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="FR-CH" style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">Phone: +41 21 693 5805<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">Address:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">EPFL STI IMX LC<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">MXD 220 (Bâtiment MXD) Station 12<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Cambria","serif";color:black;mso-fareast-language:EN-GB">1015 Lausanne, Switzerland<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="FR-CH"><o:p> </o:p></span></p>
</div>
</body>
</html>