Ncrystal

* 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 kernel, or those
with phonon VDOS curves that had large empty regions (often the case for
hydrogen VDOS curves in materials with C-H bounds). 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.

* Introduce NCMAT v4 which introduces a few new features, as described in
detail in the ncmat_doc.md file. 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 and Jose Ignacio Marquez Damian from the ESS Spallation Physics
group, and more details are available in the ncrystal GitHub issue
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.
* 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
github 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 (refer to comments in the
UO2 NCMAT file for details).
* 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.
* Expose debyeIsotropicMSD and debyeTempFromIsotropicMSD functions from
NCDebyeMSD.hh header to C and Python, allowing conversions between
atomic mean-squared-displacement and Debye temperature.
* Improve robustness of the function debyeTempFromIsotropicMSD. Previously
the internally deployed root-finding algorithm could fail under some
scenarios (e.g. non-ultra cold rubidium).
* Various improvements for ncrystal_vdos2ncmat.
* Compilation fix for pre-Catalina OSX where the aligned_alloc function is
apparently missing.
* Fix bug where early calls to removeAllDataSources could get reverted by
subsequent plugin loading.
* Before defining macros in public headers, check if present already and
if so undefine.

* RC2 for incoming release v2.6.0.

* RC1 for incoming release v2.6.0.

* The NCrystal v2.5.0 release brings major technical improvements to
NCrystal "under the hood", with around 15.000 lines of code changed in
more than 200 files! Although massive, the changes are mostly technical
in nature and mainly affects the C++ API, so people using NCrystal in
another way (e.g. through Python, C, Geant4, McStas, ANTS2, ...), should
still find that everything keeps working as before - although perhaps
with slightly improved performance and with a few new useful function
having been added to the Python/C API's.
* The list of specific changes is too long to document here, but we
have tried to provide a high-level overview of the developments
in the wiki, so please find additional information at:
https://github.com/mctools/ncrystal/wiki/Announcement-Release2.5.0

* RC2 for incoming release v2.5.0.