Hello Anas,

On Wednesday, December 21, 2005, at 09:30 AM, anas.natsheh_at_uku.fi wrote:

> Does any body knows about a way to calculate the thermal Enthalpies
> from ADF output? Is there any software doing that? I tried to
> calculated from the internal energy as in thermodynamics but the
> results were very unusual.

I will try to explain the ADF output by giving an example, in this case
for water;
there are two relevant parts:

partA gives the usual Zero-Point Vibrational energy:

  Zero-Point Energy : 0.021257 a.u.
  =================== 0.578435 eV

partB gives thermodynamic properties for a range of temperatures:
(the range of temperatures can be set within the THERMO block on input,
  by default it gives the properties at room temperature)

  ============================
  Statistical Thermal Analysis *** ideal gas assumed ***
  ============================

  Pressure: 1.000000 atm.
  Temperature: 298.150000 K

  Moments of Inertia (and direction vectors)
  ==========================================

            2.2628 4.1200 6.3828
  ------------------------------------------------
           -1.0000 0.0000 0.0000
            0.0000 0.0000 -1.0000
            0.0000 1.0000 0.0000

  The rotational contribution to the molecular entropy includes
  a term, dependent on the symmetry number sigma. The results
  reported below were computed using sigma = 2, determined
  from the point group symmetry of the input geometry (C(2V)).
  If this is not the correct symmetry, please contact SCM to
  report a bug.

      Temp Transl
    Rotat Vibrat Total
      ---- ------
    ----- ------ -----

      298.15 Entropy (cal/mole-K): 34.609
   10.485 0.007 45.101
               Internal Energy (Kcal/mole): 0.889
    0.889 13.341 15.118
               Constant Volume Heat Capacity (cal/mole-K): 2.981
    2.981 0.051 6.013

Given here are the entropy S, the internal energy U and the heat
capacity Cp;
the enthalpy H is then obtained by adding pV (=nkT, n=1) to the
internal energy U,
so in this case the enthalpy H is 15.711 kcal/mol (H=U+pV),
and the Gibbs free energy G is 2.264 kcal/mol (G=H-TS).

I hope this helps.

M.
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dr. Marcel Swart

Theoretische Chemie (kamer R152)
Vrije Universiteit Amsterdam
Faculteit der Exacte Wetenschappen

De Boelelaan 1083
1081 HV Amsterdam
The Netherlands

Tel +31-20-5987619
Fax +31-20-5987629
E-mail m.swart_at_few.vu.nl
Web http://www.few.vu.nl/~swart
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Received on 2006-01-02 19:05:43