Perturbation expansions and series acceleration procedures. Part I. ε-convergence and critical parameters |
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Authors: | M V Sangaranarayanan S K Rangarajan |
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Institution: | (1) Department of Inorganic and Physical Chemistry, Indian Institute of Science, 560 012 Bangalore, India |
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Abstract: | A simple acceleration of convergence technique known as the ‘ε-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 Padé 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. |
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Keywords: | |
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