BE Polyelectrolyte errors

[butler]

Sylvain Prevost sent the following in November 2017 (subsequently lost and refound) regarding problems with this model. He believes there are two problems:

• In the python code: concentration is rescaled from mol/dm³ to 1/ų only for monomer concentration, not for salt concentration. Further, polymer concentration is probably a misnomer for monomeric units concentration

• In the docs:
  • The definition of r₀² is wrong, { b/√(48 π L_b) } should be in the numerator, not the denominator: r₀² = b / [ α √(C_a 48 π L_b) ]
  • in the main equation, it should read r₀⁴, not r₀²
  • in the docs, the conversion of concentration from mol/dm³ to 1/ų should be explicitly indicated before any equation
  • for consistency, in the main equation, it should read (q² - 12 h/N_A C_a / b²) where N_A is Avogadro's constant (as h is supposedly in ų/mol, and assuming C_a has been converted to 1/ų