Postings for `neel': Ising model with dipolar interactions; ferromagnetic domains

• 14.2 -- 14/10/98 -- Bad Molecular Field Constants
  I have a question about one of the exercises in your book of "Simulations for SSP". Specifically it is 14.8, where one is asked to confirm the value of dipole sums quoted on p279. If I sum (a/Rij)**3 over a square lattice (with lattice constant a and excluding the origin) I should get -(\lambda + \mu)/D, which the text says is 3.9 + 6.5 = 10.4. I find by summing over the square of sites defined by -100 less than i,j less than 100 a value of 8.98. This value is essentially confirmed by Jour Chem Phys 68, 1344 (1978), where 9.034 is quoted and other references are also given.

  So I wonder if the values in the text are misprints or whether I don't understand what they represent.
  -----BS

  The values in the text, immediately above exercise 14.8, are not misprints, they're simply wrong. The correct values are (I'm pretty sure) lambda = -5.84 D and mu = -3.19 D.
  -----RHS
  postings log.

• 14.1 -- 7/25/97 (modified 8/21/97)-- Bug fix for Windows systems
  "neel" (and "ising") will crash on Windows systems if the temperature is chosen to be too low. You will soon be able to download a fix for this (and some other minor problems) from sssfix1.zip. For the time being, keep the temperature greater than 10% of the value of the energy parameters. Mac and Unix systems seem to be immune.
  postings log.