<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yiv9628606616"><div id="yui_3_16_0_1_1450866594342_3868"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;" id="yui_3_16_0_1_1450866594342_3867"><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866"><br clear="none">Does this answer work for all systems be it FCC or monoclinic or Hexagonal</div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866"><br id="yui_3_16_0_1_1450866594342_6746"></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" id="yui_3_16_0_1_1450866594342_6748" class="">"final_alat = input_alat * 0.487685488 / 0.5 = 10,345371472 bohr " where does 0.5 come from </span><br clear="none" style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" id="yui_3_16_0_1_1450866594342_6750" class=""></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class=""><br></span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_6786">If i am working on a monoclinic or Hexagonal crystal structure do i still use the 0.5 or how do i calculate the 0.5</span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class=""><br></span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_6845"> For the atomic position i got</span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_6912"><blockquote type="cite" id="yui_3_16_0_1_1450866594342_4518" class=""><div class="" role="gridcell" tabindex="0" id="yui_3_16_0_1_1450866594342_6888" style="transition: none; outline: none 0px;"><div id="yui_3_16_0_1_1450866594342_6889" style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 16px;" class=""><div class="" id="yiv8580693823yui_3_16_0_1_1450677059337_4051" style="margin: 1.2pt 0in;"><span class="" id="yiv8580693823yui_3_16_0_1_1450677059337_9769" style="font-size: 11pt; font-family: Helvetica, sans-serif;">ATOMIC POSITIONS(alat)</span></div><div class="" id="yiv8580693823yui_3_16_0_1_1450677059337_4051" style="margin: 1.2pt 0in;"><span class="" id="yiv8580693823yui_3_16_0_1_1450677059337_9774" style="font-size: 11pt; font-family: Helvetica, sans-serif;">si -0.035697193 -0.035697193 -0.035697193</span></div><div class="" id="yiv8580693823yui_3_16_0_1_1450677059337_4051" style="margin: 1.2pt 0in;" dir="ltr"><span class="" id="yiv8580693823yui_3_16_0_1_1450677059337_9779" style="font-size: 11pt; font-family: Helvetica, sans-serif;">si 0.208182292 0.208182292 0.208182292</span></div></div></div></blockquote></span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="">is there a rule to use in converting to </span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_7181">0 0 0 and 1/4 1/4 1/4 <br></span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class=""><br></span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_7464">Agbaoye Ridwan Olamide</span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_7183">Federal University of Agriculture, Abeokuta</span></div><div class="yiv9628606616qtdSeparateBR" id="yui_3_16_0_1_1450866594342_3866" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;" class="" id="yui_3_16_0_1_1450866594342_7465">M.Sc. (in view)</span></div><div class="yiv9628606616yqt7899393037" id="yiv9628606616yqt05235"></div></div></div></div><div class=".yiv9628606616yahoo_quoted"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div dir="ltr"><font size="2" face="Arial"> On Monday, December 21, 2015 1:18 AM, stefano de gironcoli <degironc@sissa.it> wrote:<br clear="none"></font></div> <br clear="none"><br clear="none"> <div class="yiv9628606616y_msg_container"><div id="yiv9628606616"><div>
<div class="yiv9628606616moz-cite-prefix">if nor celldm(1) [in Bohr] nor A [in
\AA] are given in input and the CELL_PARAMETERS card is given then
alat is defined as the length (in bohr) of the first vector in
CELL_PARAMETERS<br clear="none">
in your case 7.5*sqrt(2.0)=10.60660172 bohr<br clear="none">
<br clear="none">
if celldm(1) or A are given then the CELL_PARAMETERS are
interpreted as given in those units.<br clear="none">
In input atomic positions are given in the selected units, in
output they are always given in unit of the alat value
computed/defined in input.<br clear="none">
<br clear="none">
If you want to use AA as your input/output length unit the easiest
way is to define<br clear="none">
<br clear="none">
A=1.0 or celldm(1)=1.889726878 in the &system namelist<br clear="none">
CELL_PARAMETERS<br clear="none">
...<br clear="none">
ATOMIC_POSITIONS Angstrom [or alat since they are the same] <br clear="none">
...<br clear="none">
<br clear="none">
in output the positions and cell information will be given in
(input) alat units, that is in AA again.<br clear="none">
<br clear="none">
HTH<br clear="none">
<br clear="none">
stefano<br clear="none">
<br clear="none">
PS <br clear="none">
in your case the silicon cell contracted by<br clear="none">
0.487685488 * alat / 7.5 = 0.487685488 * sqrt(2) <br clear="none">
the final cell corresponds to an FCC with<br clear="none">
final_alat = input_alat * 0.487685488 / 0.5 = 10,345371472 bohr<br clear="none">
<br clear="none">
In these units the atomic coordinates are just <br clear="none">
0 0 0 and 1/4 1/4 1/4 (plus a small shift away from the origin due
to the fact that the center of mass remain fixed during
relaxation)<br clear="none">
<br clear="none">
<br clear="none">
<br clear="none">
On 21/12/2015 07:30, Ridwan Agbaoye wrote:<br clear="none">
</div>
<blockquote type="cite">
<div class="yiv9628606616yqt0889623001" id="yiv9628606616yqt00984"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;">
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9717" style="margin-top:1.2pt;margin-right:0in;margin-bottom:1.2pt;margin-left:0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9719" style="font-size:11pt;font-family:Helvetica, sans-serif;">Good Morning
Everybody,</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4526" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9724" style="font-size:11pt;font-family:Helvetica, sans-serif;"> </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4557" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9729" style="font-size:11pt;font-family:Helvetica, sans-serif;">I need some
help with
the interpretation of vc-relax output and conversion from
alat to bohr</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4557" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_10896" style="font-size:11pt;font-family:Helvetica, sans-serif;">I want to do
vc-relax calculation for a monoclinic system but i decide to
start with silicon a face-centered cubic system to
understand the concept of vc-relax properly </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4525" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9734" style="font-size:11pt;font-family:Helvetica, sans-serif;">I tried
vc-relax for
silicon and i got the following output </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4200" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9739" style="font-size:11pt;font-family:Helvetica, sans-serif;">Begin Final
Coordinate</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9744" style="font-size:11pt;font-family:Helvetica, sans-serif;">New Unit Cell
volume =
276.90769au^3</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9749" style="font-size:11pt;font-family:Helvetica, sans-serif;">CELL
PARAMETERS(alat=10.60660172)</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9754" style="font-size:11pt;font-family:Helvetica, sans-serif;">-0.487685488
-0.000000000 0.487685488</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9759" style="font-size:11pt;font-family:Helvetica, sans-serif;"> 0.000117363
0.487685488 0.487685488</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9764" style="font-size:11pt;font-family:Helvetica, sans-serif;">-0.487685488
0.487685488 -0.000000000</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9769" style="font-size:11pt;font-family:Helvetica, sans-serif;">ATOMIC
POSITIONS(alat)</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9774" style="font-size:11pt;font-family:Helvetica, sans-serif;">si
-0.035697193 -0.035697193 -0.035697193</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9779" style="font-size:11pt;font-family:Helvetica, sans-serif;">si
0.208182292 0.208182292 0.208182292</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9784" style="font-size:11pt;font-family:Helvetica, sans-serif;">End
of Final coordinate</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9789" style="font-size:11pt;font-family:Helvetica, sans-serif;"> </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9794" style="font-size:11pt;font-family:Helvetica, sans-serif;">My
input file has </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9799" style="font-size:11pt;font-family:Helvetica, sans-serif;"> </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9804" style="font-size:11pt;font-family:Helvetica, sans-serif;">ibrav=0
nat=2 ntyp=2</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9809" style="font-size:11pt;font-family:Helvetica, sans-serif;"> </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9814" style="font-size:11pt;font-family:Helvetica, sans-serif;">CELL
PARAMETER cubic</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9819" style="font-size:11pt;font-family:Helvetica, sans-serif;">-7.5000
0.0000 7.5000</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9824" style="font-size:11pt;font-family:Helvetica, sans-serif;">0.0000
7.5000 7.5000</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9829" style="font-size:11pt;font-family:Helvetica, sans-serif;">-7.5000
7.5000 0.0000</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9834" style="font-size:11pt;font-family:Helvetica, sans-serif;"> </span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9839" style="font-size:11pt;font-family:Helvetica, sans-serif;">How exactly do
we derive our celldm(1) and how do we convert to bohr</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" style="font-size:11pt;font-family:Helvetica, sans-serif;"><br clear="none">
</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_9844" style="font-size:11pt;font-family:Helvetica, sans-serif;">Do we need to
convert the atomic position from alat to Bohr or Angstrom</span></div>
<div class="yiv9628606616" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><span class="yiv9628606616" style="font-size:11pt;font-family:Helvetica, sans-serif;"><br clear="none">
</span></div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><font id="yiv9628606616yui_3_16_0_1_1450677059337_11772" face="Helvetica, sans-serif"><span id="yiv9628606616yui_3_16_0_1_1450677059337_11773" style="font-size:14.6666669845581px;">must i use bohr as
the unit of CELL PARAMETERS or i can use Angstrom and
declare it as CELL PARAMETER(angstrom) </span></font></div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_4051" style="margin:1.2pt 0in;"><font face="Helvetica, sans-serif"><span style="font-size:14.6666669845581px;"><br clear="none">
</span></font></div>
<div>
</div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_9848"><br clear="none">
</div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_9848"> Agbaoye
Ridwan Olamide</div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_9848"> Federal
University of Agriculture, Abeokuta</div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_9848"> M.Sc.(in view)</div>
<div class="yiv9628606616" dir="ltr" id="yiv9628606616yui_3_16_0_1_1450677059337_9848"><a rel="nofollow" shape="rect" class="yiv9628606616moz-txt-link-abbreviated" ymailto="mailto:agbaoyeridwan@yahoo.com" target="_blank" href="mailto:agbaoyeridwan@yahoo.com">agbaoyeridwan@yahoo.com</a></div>
</div></div>
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