<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=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><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:"Adobe Song Std L";
panose-1:0 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:"\@Adobe Song Std L";
panose-1:0 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:Candara;
panose-1:2 14 5 2 3 3 3 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
text-align:right;
direction:rtl;
unicode-bidi:embed;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 90.0pt 72.0pt 90.0pt;}
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-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>Dear users,<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'><o:p> </o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>I was reading the tutorial "From Wyckoff to Quantum Espresso" (can be found in google) to make sure how to correctly<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>write crystal input data. All examples seem to be using the primitive unit cell atomic positions (rather than the conventional unit cell). Is this actually so?<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'><o:p> </o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>My question is how can I know the primitive unit cell atomic positions ?<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'><o:p> </o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>I only have conventional unit cell coordinates and 3 cell parameters for a Pnma (62) crystal.<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>Also, if I use the primitive unit cell coordinates, what value should I put to celldm(1)-celldm(3) ? is it the original conventional cell one ?<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'><o:p> </o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'>Many thanks,<o:p></o:p></p><p class=MsoNormal style='text-align:left;direction:ltr;unicode-bidi:embed'><b><span style='font-family:"Candara","sans-serif";color:#00B0F0'>David Furman</span></b><b><o:p></o:p></b></p><p class=MsoNormal dir=RTL><span dir=LTR><o:p> </o:p></span></p></div></body></html>