CDEF 1.0

Compute small-angle scattering form factors for arbitrary shapes

CDEF (Computing Debye's scattering formula for Extraordinary Formfactors)

This is a Python package to approximately calculate scattering profiles of arbitrarily shaped nanoparticles for small-angle X-ray scattering (SAXS). CDEF generates a quasi-randomly distributed point cloud in the desired particle shape and then applies Debye’s formula to this ensemble of point scatterers to calculate the SAXS pattern. The shape can be loaded from an STL file. CDEF is implemented as an interface to the open source software Debyer for efficient evaluation of Debye's scattering formula. This allows the fitting of measured scattering data within reasonable time on ordinary desktop computers.

The software is described in detail in this paper.

This program was written at the Physikalisch-Technische Bundesanstalt (PTB) by Jerome Deumer and Christian Gollwitzer (2022) and is distributed under the terms of the GNU General Public License 3.0.

Usage

The usage of CDEF for computing a scattering curve and fitting measured data is demonstrated in CDEF_demo.ipynb

Installation

The recommended way is to install CDEF via pip:

pip install CDEF --user

Drop the --user if you want to install the package system-wide. To ensure you use the correct python, invoke pip as

python3 -m pip install CDEF --user

where python3 should be replaced by your Python 3 command, e.g. python3 on most Linux installations or python on Anaconda for Windows.

To install from source, go to the directory where you cloned this repository and enter the following command at the command prompt:

python3 -m pip install . --user

System requirements

CDEF should run on most systems with Python 3.6+ and requires a working C compiler compatible with Python. In addition, the following Python packages are required:

• NumPy
• SciPy
• Matplotlib

On Linux and macOS, most setups will work with the system C compiler. For Windows, the installation of a compatible C compiler is described here.

License

This program was written at the Physikalisch-Technische Bundesanstalt (PTB) by Jerome Deumer and Christian Gollwitzer (2022) and is distributed under the terms of the GNU General Public License 3.0.

CDEF is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

CDEF is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with CDEF.  If not, see <https://www.gnu.org/licenses/>.