کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5428414 | 1508673 | 2014 | 9 صفحه PDF | دانلود رایگان |
- Partition functions are computed for ammonia and phosphine.
- Calculations are performed by direct summation of millions of energy levels.
- Thermodynamic properties are computed for a wide range of temperatures.
The total internal partition function of ammonia (14NH3) and phosphine (31PH3) are calculated as a function of temperature by explicit summation of 153Â million (for PH3) and 7.5Â million (for NH3) theoretical rotation-vibrational energy levels. High accuracy estimates are obtained for the specific heat capacity, Cp, the Gibbs enthalpy function, gef, the Helmholtz function, hcf, and the entropy, S, of gas phase molecules as a function of temperature. In order to reduce the computational costs associated with the high rotational excitations, only the A-symmetry energy levels are used above a certain threshold of the total angular momentum number J. With this approach levels are summed up to dissociation energy for values of Jmax=45 and 100 for ammonia (Emax=41 051Â cmâ1) and phosphine (Emax=28 839.7Â cmâ1), respectively. Estimates of the partition function are converged for all temperatures considered for phosphine and below 3000Â K for ammonia. All other thermodynamic properties are converged to at least 2000Â K for ammonia and fully converged for phosphine.
Journal: Journal of Quantitative Spectroscopy and Radiative Transfer - Volume 142, July 2014, Pages 66-74