NCrystal release 3.2.0

This release introduces support for easy definition of custom gas mixtures, via cfg-strings like "gasmix::0.7xCO2+0.3xAr/2atm/30C", "gasmix::He/10bar/H_is_He3", "gasmix::air/0.1relhumidity", and more. Find more details on the release announcement page.

NCrystal release 3.1.0

This release focuses on those inelastic scattering events that almost bring the neutron to rest, and which are in particular important for UCN (or VCN) production in neutron moderators. The main new features are a general improvement in inelastic scattering kernel sampling for UCN or near-UCN production events, as well as a new special UCN mode which can be used for biasing or variance reduction scheme in studies involving UCN production (e.g. moderators).

Please refer to the release 3.1.0 announcement page on our wiki for a slightly more detailed overview about this new release!

NCrystal release 3.0.0

After almost a year of intense work, the NCrystal developers are very proud and excited to finally being able to present the NCrystal v3.0.0 release!

Most importantly, this release brings support for multiphase materials, material density control, SANS physics, goodies for McStas users, and various smaller but hopefully useful new features such as defining simple unstructured materials without the need for data files, new handy cfg-parameters, and other quality-of-life improvements. In addition, the release brings many other new features and technical improvements "under the hood", with around 19.000 lines of code changed in more than 300 files!

Please refer to the release 3.0.0 announcement page on our wiki for a slightly more detailed overview about this new release! Furthermore, we would like to encourage users to post questions concerning the new release (or anything else NCrystal related obviously) to the forum.

NCrystal release 2.7.3

Minor release which in addition to a few minor bug fixes, contain C++ utilities which can be used to more easily implement elastic physics described via an I(Q) curve. Refer to the CHANGELOG for more details.

NCrystal release 2.7.2

Minor release with a few compilation fixes, affecting only users of Geant4-hooks with the most recent Geant4 release (10.07.p02) or users with the rather outdated gcc 4.8.5 (cf. issue #69).

NCrystal release 2.7.1

Small bugfix release, addressing a single crystal alignment bug which was inadvertently introduced among the many technical changes in release v2.5.0, essentially swapping the meaning of @crys: and @crys_hkl: in the parts of the cfg strings defining the crystal orientation.

NCrystal release 2.7.0

With 80 new NCMAT files, the NCrystal v2.7.0 release brings the largest increase yet to the NCrystal data library, bringing it to a whooping total of 131 materials for which we provide detailed scattering of thermal neutrons! 64 of the 80 new files are crystalline materials, and the other 16 new materials are amorphous solids, which is a new material type supported with this new release. Please let us know if materials relevant for your studies are still missing in our library.

In addition to the new materials provided, several new command-line utilities for NCMAT file creation and validation are added, a few bugs fixed, and HKL-list initialisation speed was increased dramatically.

For a slightly longer but still high-level overview of the new features and materials, please visit the Announcement-Release2.7.0 page in the wiki.

In connection with this release, a special thanks goes to Kemal Ramic and Jose Ignacio Marguez Damian from the ESS Spallation Group, whose dedicated efforts have been crucial in the creation and validation of the new materials.

NCrystal release 2.6.1

Small bugfix release fixing rare numerical artifacts in some inelastic cross sections. This is not believed to have had a significant impact on any materials in the current data library, but the artifacts showed up in some of the materials being developed for the future v2.7.0 release.

Specifically, this release provides a workaround for numerical artifacts in inelastic cross sections arising from low-granularity beta-grids. In practice this affected materials which either used hard-coded low-granularity scattering kernels, or those with phonon VDOS curves that had large empty regions (for instance seen in hydrogen VDOS curves in materials with C-H bonds). The workaround for external low-granularity kernels consists of a simple "thickening" of the beta-grid, while the workaround for VDOS-based kernels consists in modifying the beta-grid generation code to ensure points are inserted into any large gaps in the single-phonon region.

NCrystal release 2.6.0

• Introduce NCMAT v4 which introduces a few new features, as described in detail on the NCMAT-format page. The most important new feature relies on the fact that it is possible to estimate atomic mean-squared-displacements directly from a phonon density of state distribution (VDOS), meaning that it is now allowed (and actually recommended) to skip @DEBYETEMPERATURE's for crystalline materials where atoms have VDOS curves available). This is not only useful, but improves low-temperature reliability of the Debye-Waller factors used in the elastic scattering components. This development was helped by Kemal Ramic (@ramic-k) and Jose Ignacio Marquez Damian (@marquezj) from the ESS Spallation Physics group, and more details are available on the related issue page (#58). The other new feature in NCMAT v4 is a new optional syntax for the @CELL section, which allows more compact specification for certain crystal systems (in particular cubic systems).
• The vast majority of crystalline materials in the NCrystal data library were updated to take advantage of the new features, and in addition the number of VDOS curves was increased dramatically, meaning that the dynamics in almost all crystalline materials are now described using actual VDOS curves rather than just Debye temperatures. The Data-library page of the wiki has been updated accordingly, and in brief the modified materials are:
  • Missing VDOS curves for all elements in beryllium-fluoride (BeF2), aragonite (CaCO3), cuprite (Cu2O), periclase (MgO), and quartz (SiO2) were provided by Kemal Ramic from the ESS Spallation Physics group, based on modelling with Phonopy, VASP and OCLIMAX software.
  • Missing VDOS curves for 14 mono-atomic materials were added (fixing issue #39): Au, Ba, Cr, Mg, Mo, Na, Nb, Pd, Pt, Rb, Sc, Sn, Y, and Zn. Refer to comments in the individual NCMAT files for references concerning the origin of these curves.
  • Missing VDOS curves were added to uranium oxide (UO2), taken from DOI:10.1103/PhysRevB.102.134312. Note that UO2 NCMAT files with VDOS tuned for specific temperatures are available in the ncrystal-extra repo.
  • All existing files with VDOS have been update to NCMAT v4, and had @DEBYETEMPERATURE sections removed in order to benefit from the better performance of getting the atomic displacements from the VDOS.
  • Added new material: gamma-Iron (Fe_sg225_Iron-gamma.ncmat) with VDOS curve. At the same time, the not particularly useful beta-Iron file was removed, so the NCrystal data library now contains both alpha- and gamma-iron, both with VDOS curves.
• A few other issues were addressed, for details refer to the CHANGELOG.

NCrystal release 2.5.0

The NCrystal developers are happy to announce the NCrystal v2.5.0 release. This release brings major technical improvements to NCrystal "under the hood", with around 15.000 lines of code changed in more than 200 files!

As the changes are numerous, we have tried to provide a high-level overview of them on the Announcement-Release2.5.0 page in the wiki.