Signals the use of neutron atomic scattering lengths.Scattering lengths for isotopes can be used by placing the isotope name after “occ” as in:

occ 6Li 1

occ 36Ar 1

The scattering lengths data, contained in the file NEUTSCAT.CPP, is from


Constant wavelength neutron diffraction requires a Lorentz correction using the Lorentz_Factor  macro (defined in TOPAS.INC); it is defined as follows:

scale_pks = 1 / (Sin(Th)^2 Cos(Th));


Surpresses LIMIT_MIN and LIMIT_MAX warning messages.


If defined then site fractional coordinates are normalized. Normalization of a particular fractional coordinate does not occur if it has min/max limits, is part of a rigid body or part of a site constraint of any kind.

[numerical_area E]

Returns the numerically calculated area under the phase.

Personal Tools