[Wien] total energy value too high

[Paula R. Alonso]

Free energy 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.
You obtain total energy in Ry/cell. You must first convert it to Ry/at. Then, 1Ry/at = 13.13 x 10^5 Joule/ mole .
Paula Alonso

Departamento de Materiales - Centro Atómico Constituyentes
Comisión Nacional de Energía Atómica
Avda Gral Paz 1499, San Martín, Buenos Aires, CP B1650KNA
 Argentina.
  ----- Original Message ----- 
  From: Chandrika 
  To: Wien at zeus.theochem.tuwien.ac.at 
  Sent: Monday, September 26, 2005 3:40 AM
  Subject: [Wien] total energy value too high


  Hello Wien Users,
  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. (i) I presumed that the value derived by Wien is Ry per unit cell. Is that correct?
  (i) Therefore to convert to kcal/mole, I used 1Ry = 13.13 x 10^5 Joule/ mole . Is this okay?
  (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.
  Could anyone suggest where I have gone wrong?
  I would particularly like to know about the conversion units.
  Thanks in advance.
  Chandrika
  -----------------------------------------------------------------------------------------
  Dr (Ms) Chandrika Varadachari
  Raman Centre for Applied and Interdisciplinary Sciences
  16A Jheel Road
  Calcutta 700075
  India
  Tel : 91-33-24830029
  Fax : 91-33-24180610
  web : www.rcais.org.in


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