The Madelung constant (in absolute value).
(for the NaCl)
References :
Richard E. Crandall, Topics in Advanced Scientific Computation,
Springer , Telos books, 1996. pages 73-79.
Andre Hautot, New applications of Poisson's summation formula, J of Phys, A vol. 8 #6, 1975 pp 853-862.
David H. Bailey, personal communication,
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The gamma function has a minumum at this point.
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