Changeset c1e44e5 in sasmodels for sasmodels/models/hayter_msa.py
- Timestamp:
- Mar 29, 2019 11:59:45 PM (5 years ago)
- Branches:
- master
- Children:
- a42b091
- Parents:
- 663d2a8
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sasmodels/models/hayter_msa.py
r9947865 rc1e44e5 1 1 # Note: model title and parameter table are inserted automatically 2 2 r""" 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 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 7 repulsion between the charged particles. 8 8 9 9 .. note:: 10 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 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 13 the :ref:`hardsphere` $S(q)$ instead. The upper limit for the charge 14 14 is limited to 200e to avoid numerical instabilities. 15 15 16 16 .. note:: 17 17 18 Earlier versions of SasView did not incorporate the so-called 19 $\beta(q)$ ("beta") correction [3] for polydispersity and non-sphericity. 18 Earlier versions of SasView did not incorporate the so-called 19 $\beta(q)$ ("beta") correction [3] for polydispersity and non-sphericity. 20 20 This is only available in SasView versions 4.2.2 and higher. 21 21 22 22 The salt concentration is used to compute the ionic strength of the solution 23 which in turn is used to compute the Debye screening length. There is no 24 provision for entering the ionic strength directly. **At present the 25 counterions are assumed to be monovalent**, though it should be possible 26 to simulate the effect of multivalent counterions by increasing the salt 23 which in turn is used to compute the Debye screening length. There is no 24 provision for entering the ionic strength directly. **At present the 25 counterions are assumed to be monovalent**, though it should be possible 26 to simulate the effect of multivalent counterions by increasing the salt 27 27 concentration. 28 28 29 Over the range 0 - 100 C the dielectric constant $\kappa$ of water may be 30 approximated with a maximum deviation of 0.01 units by the empirical 29 Over the range 0 - 100 C the dielectric constant $\kappa$ of water may be 30 approximated with a maximum deviation of 0.01 units by the empirical 31 31 formula [4] 32 32 … … 34 34 35 35 \kappa = 87.740 - 0.40008 T + 9.398x10^{-4} T^2 - 1.410x10^{-6} T^3 36 36 37 37 where $T$ is the temperature in celsius. 38 38 … … 63 63 .. [#] C G Malmberg and A A Maryott, *J. Res. Nat. Bureau Standards*, 56 (1956) 2641 64 64 65 Source66 ------67 68 `hayter_msa.py <https://github.com/SasView/sasmodels/blob/master/sasmodels/models/hayter_msa.py>`_69 70 `hayter_msa.c <https://github.com/SasView/sasmodels/blob/master/sasmodels/models/hayter_msa.c>`_71 72 65 Authorship and Verification 73 66 ---------------------------- 74 67 75 * **Author:** 76 * **Last Modified by:** 68 * **Author:** 69 * **Last Modified by:** 77 70 * **Last Reviewed by:** Steve King **Date:** March 28, 2019 78 * **Source added by :** Steve King **Date:** March 25, 201979 71 """ 80 72 … … 101 93 [Hayter-Penfold RMSA charged sphere interparticle S(Q) structure factor] 102 94 Interparticle structure factor S(Q) for charged hard spheres. 103 This routine only works for charged particles! For uncharged particles 104 use the hardsphere S(q) instead. The "beta(q)" correction is available 95 This routine only works for charged particles! For uncharged particles 96 use the hardsphere S(q) instead. The "beta(q)" correction is available 105 97 in versions 4.2.2 and higher. 106 98 """ … … 110 102 # [ "name", "units", default, [lower, upper], "type", "description" ], 111 103 # 112 # NOTE: SMK, 28Mar19 The upper limit for charge is set to 200 to avoid instabilities noted by PK in 113 # Ticket #1152. Also see the thread in Ticket 859. The docs above also note that charge=0 will 104 # NOTE: SMK, 28Mar19 The upper limit for charge is set to 200 to avoid instabilities noted by PK in 105 # Ticket #1152. Also see the thread in Ticket 859. The docs above also note that charge=0 will 114 106 # cause problems, yet the default parameters allowed it! After discussions with PK I have 115 # changed it to (an arbitarily) small but non-zero value. But I haven't changed the low limit 107 # changed it to (an arbitarily) small but non-zero value. But I haven't changed the low limit 116 108 # in function random() below. 117 109 #
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