Email: robert.rambo@diamond.ac.uk
Tel: +44 (0)1235 56 7675
A summary of the models available in FISH
MODEL (LM) | LTYP | Models in FISH |
| | PARTICLE FORM FACTORS |
1 | 1 | Spherical particle - simple monodisperse solid sphere |
12 | 1 | Guinier radius ( direct fit, useful to include flat background) |
10 or 8 | 1 | Spherical shell, sharp step ( repeat for multiple shells ) |
10 or 8 | 11 | Spherical shell, linear, diffuse step |
10 or 8 | 21 | Spherical shell, decreasing exponential, to infinity |
10 or 8 | 31 | Spherical shell, decreasing exponential, truncated |
10 or 8 | 41 | Spherical shell, increasing exponential from R=0 |
10 or 8 | 51 | Spherical shell, increasing exponential, from previous R |
9 | 1 | square operation, use after model 8 monodisperse shells |
18 | 1 | Rod/disc - rigid, monodisperse, randomly oriented, core/shell, with shell at ends (useful for core/shell disc ) |
18 | 11 | Rod/disc - rigid, randomly oriented, core/shell, without shell at ends (useful for hollow cylinder) |
18 | 21 & 31 | Rods, as above, oriented in shear flow, Hayter & Penfold, fit to 1d averaged wedges of 2d data. |
18 | 41 & 51 | Rods, as above, nematic “Maier-Saupe, DeGennes” distribution. |
18 | 61 & 71 | Rods, as above, nematic “Maier-Saupe, DeGennes” distribution, viewed end-on. |
1 | 11 | "end on" view of a monodisperse cylinder |
10 or 8 | 61 | End-on view of mono/polydisperse fixed rod, multi-shell, sharp step |
21 | 1 | Solid ellipsoid, use model 24 instead. |
24 | 1 | Ellipsoid, core/shell with outer/inner radius ratio constant |
24 | 11 | Ellipsoid, core/shell with constant thickness shell |
24 | 21 &31 | Ellipsoids as above, but with molecular constraints for surfactant micelles. |
| | POLYDISPERSITY used with Model 10 |
1 | 21 | Polydisperse solid spheres - analytic equations for Schultz distribution |
6 | 11 | Schultz distribution (all model 6 use numerical integration) |
6 | 21 | symmetric parabola |
6 | 31 | triangular decreasing |
6 | 41 | concave decreasing |
6 | 51 | flat “hat” |
6 | 1 | cubic polynomial |
6 | 61 | alternative cubic polynomial |
6 | 71 | stick model ( for bimodal ) |
6 | 81 | power law between R1 & R2 |
6 | 91 | log-normal distribution |
5 | 1 | test of a maximum entropy condition on polydispersity |
| | PARTICLE STRUCTURE FACTORS |
7 | 1 | Critical scattering “attractive” S(Q) |
19 | 1 | Correlation hole S(Q) |
22 | 1 | Hard sphere S(Q) |
22 | 11 | Hard sphere S(Q) with attractive/repulsive square well |
23 | 1 | Hayter-Penfold charged sphere S(Q) (using their routines) |
25 | 1 | as model 23, with additional critical scattering term. |
11 | 21 | P(Q) = Constant ( useful for fitting just S(Q) ) |
| | POLYMERS |
14 | 1 | Debye Gaussian coil - for polymers |
14 | 11 | Polydisperse Debye Gaussian coil |
14 | 21 | attempt at Kratky-Porod worm-like persistence chain, (14 - 71 is better) |
14 | 31 | Benoit f-branched star Debye coil |
14 | 41 | Dozier star polymer |
14 | 51 | Leibler diblock copolymer |
14 | 61 | H-shaped copolymer with deuterated tips (D.J.Read) |
14 | 71 | Kholodenko worm – mono/polydisperse with Guinier Raxial |
14 | 81 | Kholodenko worm – mono/polydisperse with core/shell rod |
| | SURFACES, SHEETS & FRACTALS |
20 | 1 | Q**n term ( compare LM=11 ) |
12 | 11 | Porod surface, with optional diffuse interface |
12 | 21 | Porod surface, with diffuse layer of different scattering density. |
26 | 1 | Surface fractal form factor |
13 | 1 | Volume fractal S(Q) |
26 | 11 | Andrew Allen, “cement” surface fractal |
13 | 11 | Andrew Allen “cement” volume fractal |
28 | 1 & 11 | Polydisperse sheet, with Lorentz “waviness” |
28 | 21 | Core/shell sheet, with Lorentz “waviness” |
28 | 31 | Core/exponential shell sheet, with Lorentz “waviness” |
29 | 1 | One dimensional paracrystalline stack, Kotlarchyk & Ritzau. (useful even for a bilayer ) |
29 | 11 | Wenig & Bramer, flat, 3 phase paracrystal, allows gaps between stacks to have different scattering densities |
| | GENERIC GELS & 2 PHASE MODELS |
16 | 1 &11 | Teubner & Strey 2 phase “peak” |
17 | 11 | Debye random 2 phase |
27 | 1 | Gels - Lorentzian plus Debye-Beuche |
| | PEAK FITTING |
27 | 21 | Gaussian peak |
27 | 71 | Stretched Gaussian peak ( as used for LOQ resolution) |
27 | 31 | Voigt peak ( Gaussian convoluted with Lorentzian) |
27 | 51 | Gaussian peak, going to exponential, with continuous first derivative. |
27 | 61 | Ikeda-Carpenter equation for neutron moderator time distributions |
27 | 81 | Gaussian convoluted by exponential |
| | QUASIELASTIC |
4 | 11 | “Vanadium” resolution function for neutron quasielastic scattering |
11 | 31 | Delta function, as alternative to LM=4, LTYP=11 for quasielastic data. |
27 | 11 | Lorentzian, for quasielastic neutrons |
| | GENERAL |
2 | 1 | does nothing - allows parameters to be introduced into constraints |
3 | 11 | Simple flat background ( note background is stored separately and is not resolution smeared) |
3 | 1 | Quadratic background |
11 | 1 | General polynomial to order 7 |
4 | 1 | Scaled subtraction of a “background” data set. |
11 | 21 | P(Q) = Constant ( useful for fitting just S(Q) ) |
15 | 21 &31 | Resolution smearing by a constant width Gaussian |
15 | 41 | Resolution smearing by input curve |
15 | 51,61 & 71 | Resolution smearing, estimated for LOQ at ISIS |
5 | -n | Predicate observation - allows weighting of parameters towards “known” values, see manual. |
88 | 0 or n | Allows multiple data sets, following lines are for all (0) or just set n. |
99 | 1 | ALWAYS needed to end the calculation |
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