Perturbation expansions and series acceleration procedures. Part I. ε-convergence and critical parameters

Autor: M V Sangaranarayanan, S K Rangarajan
Rok vydání: 1984
Předmět:
Zdroj: Pramana. 22:183-201
ISSN: 0973-7111
0304-4289
DOI: 10.1007/bf02846372
Popis: A simple acceleration of convergence technique known as the ‘e-convergence algorithm’ (ea) is applied to determine the critical temperatures and exponents. Several illustrations involving well-known series expansions appropriate to two- and three-dimensional Ising models, three-dimensional Heisenberg models, etc., are given. Apart from this, a few recently studied ferrimagnetic systems have also been analysed to emphasise the generality of the approach. Where exact solutions are available, our estimates obtained from this procedure are in excellent agreement. In the case of other models, the critical parameters we have obtained are consistent with other estimates such as those of the Pade approximants and group theoretic methods. The same procedure is applied to the partial virial series for hard spheres and hard discs and it is demonstrated that the divergence of pressure occurs when the close-packing density is reached. The asymptotic form for the virial equation of state is found to beP/ρkT ∼ (1 −ρ/ρ c −1 for hard spheres and hard discs. Apart from the estimation of ‘critical parameters’, we have applied theea and the parametrised Euler transformation to sum the partial, truncated virial series for hard spheres and hard discs. The resulting values of pressure so obtained, compare favourably with the molecular dynamics results.
Databáze: OpenAIRE
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