Changeset 3b8a004 in sasmodels
- Timestamp:
- Jun 28, 2018 11:15:49 AM (6 years ago)
- Branches:
- master, core_shell_microgels, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
- Children:
- 05cd67f
- Parents:
- 4476951
- File:
-
- 1 edited
Legend:
- Unmodified
- Added
- Removed
-
sasmodels/models/guinier.py
r4476951 r3b8a004 21 21 22 22 Note that $R_g^2$ may be negative, which happens when a form factor $P(Q)$ is 23 increasing with $Q$ rather than decreasing. This can occur for core orshell23 increasing with $Q$ rather than decreasing. This can occur for core/shell 24 24 particles, hollow particles, or for composite particles with domains of 25 25 different SLDs in a solvent with an SLD close to the average match point. 26 (Alternatively, itmight be regarded as there being an internal inter-domain26 (Alternatively, this might be regarded as there being an internal inter-domain 27 27 "structure factor" within a single particle which gives rise to a peak in the 28 28 scattering). 29 29 30 30 To specify a negative value of $R_g^2$ in SasView, simply give $R_g$ a negative 31 value ($R_g^2$ will be evaluated as $R_g |R_g|$). 32 33 Note that the physical radius of gyration, of the exterior of the particle, 34 will still be large and positive. It is only the apparent size from the small 35 $Q$ data that will give a small or negative value of $R_g^2$. 31 value ($R_g^2$ will be evaluated as $R_g |R_g|$). Note that the physical radius 32 of gyration, of the exterior of the particle, will still be large and positive. 33 It is only the apparent size from the small $Q$ data that will give a small or 34 negative value of $R_g^2$. 36 35 37 36 References … … 81 80 82 81 # parameters for demo 83 demo = dict(scale=1.0, rg=60.0)82 demo = dict(scale=1.0, background=0.001, rg=60.0 ) 84 83 85 84 # parameters for unit tests
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