Inform about expected sign of Im(SLD)
Original title: A negative imaginary SLD crashes the Python interface.
Running the following
import bornagain as ba
ba.MaterialBySLD('A', 2.418, -1.0)
Will crash the python interface. The following is returned in the terminal
libc++abi.dylib: terminating with uncaught exception of type std::runtime_error: The imaginary part of the SLD must be greater or equal zero
An imaginary SLD can be less than zero, ie. from https://www.ncnr.nist.gov/resources/activation/ B has an imaginary scattering length density of -0.278. It is possible I am overlooking something for this.
Edited by Wuttke, Joachim