I D Feranchuk and A A Ivanov 2004 J. Phys. A: Math. Gen. 37 9841 doi:10.1088/0305-4470/37/42/001
I D Feranchuk1 and A A Ivanov1,2
Show affiliationsOperator method and cumulant expansion are used for nonperturbative calculation of the partition function and the free energy in quantum statistics. It is shown for Boltzmann diatomic molecular gas with some model intermolecular potentials that the zeroth-order approximation of the proposed method interpolates the thermodynamic values with rather good accuracy in the entire range of both the Hamiltonian parameters and temperature. The systematic procedure for calculation of the corrections to the zeroth-order approximation is also considered.
02.60.Gf Algorithms for functional approximation
03.65.Db Functional analytical methods
05.70.Ce Thermodynamic functions and equations of state
03.65.Yz Decoherence; open systems; quantum statistical methods
Issue 42 (22 October 2004)
Received 10 January 2004, in final form 2 June 2004
Published 6 October 2004
I D Feranchuk and A A Ivanov 2004 J. Phys. A: Math. Gen. 37 9841
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