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<DIV><FONT face=Arial size=2>Free energy </FONT><FONT face=Arial size=2>of
formation is referred to the pure structures. You have to substrat from the
total energy of the compound the total energy of the pure elements in the same
structure, weighted by atomic fraction.</FONT></DIV>
<DIV><FONT face=Arial size=2>You obtain total energy in Ry/cell. You must
first convert it to Ry/at. T</FONT><FONT face=Arial size=2>hen, 1Ry/at
</FONT><FONT face=Arial size=2>= 13.13 x 10^5 Joule/
mole .</FONT></DIV>
<DIV><FONT face=Arial size=2>Paula Alonso</FONT></DIV>
<DIV> </DIV>
<DIV>Departamento de Materiales – Centro Atómico Constituyentes</DIV>
<DIV>Comisión Nacional de Energía Atómica</DIV>
<DIV>Avda Gral Paz 1499, San Martín, Buenos Aires, CP B1650KNA</DIV>
<DIV> Argentina.</DIV>
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<DIV style="FONT: 10pt arial">----- Original Message -----
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<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=rcais@cal3.vsnl.net.in
href="mailto:rcais@cal3.vsnl.net.in">Chandrika</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=Wien@zeus.theochem.tuwien.ac.at
href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, September 26, 2005 3:40
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Wien] total energy value too
high</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Hello Wien Users,</FONT></DIV>
<DIV><FONT face=Arial size=2>I am trying to derive the total energy of SiC in
order to later derive its standard free energy of formation. With all three
options in Wien2k 05 (13, 14 and 5) I get values near -656 Ry.
</FONT><FONT face=Arial size=2>(i) I presumed that the value derived by Wien
is Ry <EM>per unit cell</EM>. Is that correct?</FONT></DIV>
<DIV><FONT face=Arial size=2>(i) Therefore to convert to kcal/mole, I
used 1Ry = 13.13 x 10^5 Joule/ mole . Is this okay?</FONT></DIV>
<DIV><FONT face=Arial size=2>(iii) The derived value of total energy of SiC is
then -861300 KJoule/mole. This is several orders of magnitude higher than
the free energy of formation of SiC which is -72.2 KJoule/mole.</FONT></DIV>
<DIV><FONT face=Arial size=2>Could anyone suggest where I have gone
wrong?</FONT></DIV>
<DIV><FONT face=Arial size=2>I would particularly like to know about the
conversion units.</FONT></DIV>
<DIV><FONT face=Arial size=2>Thanks in advance.</FONT></DIV>
<DIV><FONT face=Arial size=2>Chandrika</FONT></DIV>
<DIV><FONT face=Arial
size=2>-----------------------------------------------------------------------------------------<BR>Dr
(Ms) Chandrika Varadachari<BR>Raman Centre for Applied and Interdisciplinary
Sciences<BR>16A Jheel Road<BR>Calcutta 700075<BR>India<BR>Tel :
91-33-24830029<BR>Fax : 91-33-24180610<BR>web : <A
href="http://www.rcais.org.in">www.rcais.org.in</A></FONT></DIV>
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