[Wien] total energy value too high

[Chandrika]

Dear Paula,
Many thanks for the suggestion.
Does this mean that I should do total energy derivations for (i) a structure containing only Si (ii) a structure containing only C and (iii) subtract from the total energy for SiC. 
Or are these values available within the derivations for SiC itself?
Thank you,
Chandrika
  ----- Original Message ----- 
  From: Paula R. Alonso 
  To: A Mailing list for WIEN2k users 
  Sent: Monday, September 26, 2005 9:07 PM
  Subject: RE: [Wien] total energy value too high


  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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