JANA2006 is a freely available program for structure determination of standard, modulated and magnetic samples based on X-ray or neutron single crystal/ powder diffraction or on electron diffraction. The system has been developed for 30 years from specialized tool for refinement of modulated structures to a universal program covering standard as well as advanced crystallography. The aim of this article is to describe the basic features of JANA2006 and explain its scope and philosophy. It will also serve as a basis for future publications detailing tools and methods of JANA.

We present the crystallographic program Jana2020, the successor of Jana2006. Jana2020 has new, technically different graphics and structure plot-driven intuitive control. Tools known from Jana2006 were revised and inserted into a new logical scheme, and their control connected with the structure plot. Some of the tools were considerably improved. We focus on the details of the most dynamically developing parts, namely twinned structures, magnetic structures, and structure analysis based on electron diffraction data.

Phases with spontaneous time-reversal ( $${{{{{{{\mathcal{T}}}}}}}}$$T ) symmetry breaking are sought after for their anomalous physical properties, low-dissipation electronic and spin responses, and information-technology applications. Recently predicted altermagnetic phase features an unconventional and attractive combination of a strong $${{{{{{{\mathcal{T}}}}}}}}$$T -symmetry breaking in the electronic structure and a zero or only weak-relativistic magnetization. In this work, we experimentally observe the anomalous Hall effect, a prominent representative of the $${{{{{{{\mathcal{T}}}}}}}}$$T -symmetry breaking responses, in the absence of an external magnetic field in epitaxial thin-film Mn₅Si₃ with a vanishingly small net magnetic moment. By symmetry analysis and first-principles calculations we demonstrate that the unconventional d-wave altermagnetic phase is consistent with the experimental structural and magnetic characterization of the Mn₅Si₃ epilayers, and that the theoretical anomalous Hall conductivity generated by the phase is sizable, in agreement with experiment. An analogy with unconventional d-wave superconductivity suggests that our identification of a candidate of unconventional d-wave altermagnetism points towards a new chapter of research and applications of magnetic phases.

Single-crystal x-ray diffraction data on the 2:2:1:2 Bi-Sr-Ca-Cu-O superconducting phase have been used in a four-dimensional refinement of the modulations of both the metal and oxygen atoms. An expression for an analytical temperature-factor modulation function has been derived and applied to the bismuth atoms. The large value of the temperature factor of Bi in some of the unit cells indicates a contribution from static disorder. The modulation of the oxygen atoms in the bismuth layer is best described by a function that allows the displacement to vary linearly with unit-cell position and incorporates the possibility of excess oxygen near the end of a modulation period. The results on oxygen occupancy and the behavior of the Bi temperature factor are compatible with models that attribute the origin of the modulation to the existence of extra oxygen atoms in the Bi-O layers. Refinement in the noncentrosymmetric super space group M:A2aa:1¯11 leads to significantly better results than the centrosymmetric treatment.