Changeset 5f3c534 in sasmodels for sasmodels/models/hayter_msa.py
- Timestamp:
- Mar 27, 2019 10:11:45 AM (5 years ago)
- Branches:
- master, core_shell_microgels, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
- Children:
- 9947865
- Parents:
- 055ec4f
- File:
-
- 1 edited
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sasmodels/models/hayter_msa.py
r0507e09 r5f3c534 1 1 # Note: model title and parameter table are inserted automatically 2 2 r""" 3 This calculates the structure factor (the Fourier transform of the pair 4 correlation function $g(r)$) for a system of charged, spheroidal objects 5 in a dielectric medium. When combined with an appropriate form factor 6 (such as sphere, core+shell, ellipsoid, etc), this allows for inclusion 7 of the interparticle interference effects due to screened coulomb repulsion 8 between charged particles. 3 Calculates the interparticle structure factor for a system of charged, 4 spheroidal, objects in a dielectric medium [1,2]. When combined with an 5 appropriate form factor $P(q)$, this allows for inclusion of the 6 interparticle interference effects due to screened Coulombic 7 repulsion between the charged particles. 9 8 10 **This routine only works for charged particles**. If the charge is set to 11 zero the routine may self-destruct! For non-charged particles use a hard 12 sphere potential. 9 .. note:: 10 11 This routine only works for charged particles! If the charge is set 12 to zero the routine may self-destruct! For uncharged particles use 13 the :ref:`hardsphere` $S(q)$ instead. 14 15 .. note:: 16 17 Earlier versions of SasView did not incorporate the so-called 18 $\beta(q)$ ("beta") correction [3] for polydispersity and non-sphericity. 19 This is only available in SasView versions 4.2.2 and higher. 13 20 14 21 The salt concentration is used to compute the ionic strength of the solution 15 which in turn is used to compute the Debye screening length. At present16 there is no provision for entering the ionic strength directly nor for use 17 of any multivalent salts, though it should be possible to simulate the effect 18 of this by increasing the salt concentration. The counterions are also 19 assumed to be monovalent.22 which in turn is used to compute the Debye screening length. There is no 23 provision for entering the ionic strength directly. **At present the 24 counterions are assumed to be monovalent**, though it should be possible 25 to simulate the effect of multivalent counterions by increasing the salt 26 concentration. 20 27 21 In sasview the effective radius may be calculated from the parameters 28 Over the range 0 - 100 C the dielectric constant $\kappa$ of water may be 29 approximated with a maximum deviation of 0.01 units by the empirical 30 formula [4] 31 32 .. math:: 33 34 \kappa = 87.740 - 0.40008 T + 9.398x10^{-4} T^2 - 1.410x10^{-6} T^3 35 36 where $T$ is the temperature in celsius. 37 38 In SasView the effective radius may be calculated from the parameters 22 39 used in the form factor $P(q)$ that this $S(q)$ is combined with. 23 40 … … 38 55 39 56 .. [#] J B Hayter and J Penfold, *Molecular Physics*, 42 (1981) 109-118 57 40 58 .. [#] J P Hansen and J B Hayter, *Molecular Physics*, 46 (1982) 651-656 59 60 .. [#] M Kotlarchyk and S-H Chen, *J. Chem. Phys.*, 79 (1983) 2461-2469 61 62 .. [#] C G Malmberg and A A Maryott, *J. Res. Nat. Bureau Standards*, 56 (1956) 2641 41 63 42 64 Source … … 52 74 * **Author:** 53 75 * **Last Modified by:** 54 * **Last Reviewed by:** 76 * **Last Reviewed by:** Steve King **Date:** March 27, 2019 55 77 * **Source added by :** Steve King **Date:** March 25, 2019 56 78 """ … … 74 96 75 97 name = "hayter_msa" 76 title = "Hayter-Penfold rescaled MSA, charged sphere, interparticle S(Q) structure factor"98 title = "Hayter-Penfold Rescaled Mean Spherical Approximation (RMSA) structure factor for charged spheres" 77 99 description = """\ 78 100 [Hayter-Penfold RMSA charged sphere interparticle S(Q) structure factor] 79 Interparticle structure factor S(Q)for a charged hard spheres. 80 Routine takes absolute value of charge, use HardSphere if charge 81 goes to zero. 82 In sasview the effective radius and volume fraction may be calculated 83 from the parameters used in P(Q). 101 Interparticle structure factor S(Q) for charged hard spheres. 102 This routine only works for charged particles! For uncharged particles 103 use the hardsphere S(q) instead. The "beta(q)" correction is available 104 in versions 4.2.2 and higher. 84 105 """ 85 106 … … 93 114 ["temperature", "K", 318.16, [0, 450], "", "temperature, in Kelvin, for Debye length calculation"], 94 115 ["concentration_salt", "M", 0.0, [0, inf], "", "conc of salt, moles/litre, 1:1 electolyte, for Debye length"], 95 ["dielectconst", "None", 71.08, [-inf, inf], "", "dielectric constant (relative permittivity) of solvent, default water, for Debye length"]116 ["dielectconst", "None", 71.08, [-inf, inf], "", "dielectric constant (relative permittivity) of solvent, kappa, default water, for Debye length"] 96 117 ] 97 118 # pylint: enable=bad-whitespace, line-too-long
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