1 | .. _HayterMSAsq:
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2 |
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3 | HayterMSAsq
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4 | =======================================================
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5 |
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6 | Hayter-Penfold MSA charged sphere interparticle S(Q) structure factor
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7 |
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8 | ============= ================================================================ ======= =============
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9 | Parameter Description Units Default value
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10 | ============= ================================================================ ======= =============
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11 | scale Source intensity None 1
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12 | background Source background |cm^-1| 0
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13 | effect_radius effective radius of hard sphere |Ang| 20.75
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14 | charge charge on sphere (in electrons) e 19
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15 | volfraction volume fraction of spheres None 0.0192
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16 | temperature temperature, in Kelvin, for Debye length calculation K 318.16
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17 | saltconc conc of salt, 1:1 electolyte, for Debye length M 0
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18 | dielectconst dielectric constant of solvent (default water), for Debye length None 71.08
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19 | ============= ================================================================ ======= =============
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20 |
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21 | The returned value is a dimensionless structure factor, $S(q)$.
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22 |
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23 |
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24 | This calculates the structure factor (the Fourier transform of the pair
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25 | correlation function $g(r)$) for a system of charged, spheroidal objects
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26 | in a dielectric medium. When combined with an appropriate form factor
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27 | (such as sphere, core+shell, ellipsoid, etc), this allows for inclusion
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28 | of the interparticle interference effects due to screened coulomb repulsion
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29 | between charged particles.
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30 |
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31 | **This routine only works for charged particles**. If the charge is set to
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32 | zero the routine will self-destruct! For non-charged particles use a hard
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33 | sphere potential.
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34 |
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35 | The salt concentration is used to compute the ionic strength of the solution
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36 | which in turn is used to compute the Debye screening length. At present
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37 | there is no provision for entering the ionic strength directly nor for use
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38 | of any multivalent salts. The counterions are also assumed to be monovalent.
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39 |
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40 | For 2D data, the scattering intensity is calculated in the same way as 1D,
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41 | where the $q$ vector is defined as
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42 |
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43 | .. math::
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44 |
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45 | q = \sqrt{q_x^2 + q_y^2}
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46 |
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47 | .. figure:: img/HayterMSAsq_227.jpg
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48 |
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49 | 1D plot using the default values (in linear scale).
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50 |
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51 | **References**
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52 |
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53 | J B Hayter and J Penfold, *Molecular Physics*, 42 (1981) 109-118
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54 |
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55 | J P Hansen and J B Hayter, *Molecular Physics*, 46 (1982) 651-656
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56 |
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