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Recent advances in quantum crystallography have shown that, beyond conventional charge density refinement, a one‐electron reduced density matrix (1‐RDM) satisfying N‐representability conditions can be reconstructed using jointly experimental X‐ray structure factors and directional Compton profiles (DCP) through semidefinite programming. So far, such reconstruction methods for 1‐RDM, not constrained to idempotency, have been tested only on a toy model system (CO2). In this work, a new method is assessed on crystalline urea [CO(NH2)2] using static (0 K) and dynamic (50 K) artificial experimental data. An improved model, including symmetry constraints and frozen core‐electron contribution, is introduced to better handle the increasing system complexity. Reconstructed 1‐RDMs, deformation densities and DCP anisotropy are analysed, and it is demonstrated that the changes in the model significantly improve the reconstruction quality, even when there is insufficient information and data corruption. The robustness of the model and the strategy are thus shown to be well adapted to address the reconstruction problem from actual experimental scattering data. [ABSTRACT FROM AUTHOR]

The positions of the figurative points on the triangular Gibbs phase diagram for the process of high-temperature synthesis of solid solutions LiyNi2−yO2 were determined for the first time using a combination of x-ray diffraction (XRD) and Compton scattering methods. The trajectory of the figurative point is built according to experimental data for temperatures of 650 and 750 °C. The ratios of the phases in equilibrium are found. It was established that, when the structure goes from rock salt to layered structures, the composition of the reagent mixture changes nonmonotonically: with an increase in the degree of ordering of the solid solution lattice, the sum molecular weight of the solid reagents increases. It has been shown experimentally that the combined use of XRD and Compton scattering makes it possible to carry out physicochemical analysis of the process and predict the final product. [ABSTRACT FROM AUTHOR]

This article retraces different methods that have been explored to account for the atomic thermal motion in the reconstruction of one‐electron reduced density matrices from experimental X‐ray structure factors (XSF) and directional Compton profiles (DCP). Attention has been paid to propose the simplest possible model, which obeys the necessary N‐representability conditions, while accurately reproducing all available experimental data. The deconvolution of thermal effects makes it possible to obtain an experimental static density matrix, which can directly be compared with theoretical 1‐RDM (reduced density matrix). It is found that above a 1% statistical noise level, the role played by Compton scattering data becomes negligible and no accurate 1‐RDM is reachable. Since no thermal 1‐RDM is available as a reference, the quality of an experimentally derived temperature‐dependent matrix is difficult to assess. However, the accuracy of the obtained static 1‐RDM, through the performance of the refined observables, is strong evidence that the Semi‐Definite Programming method is robust and well adapted to the reconstruction of an experimental dynamical 1‐RDM. [ABSTRACT FROM AUTHOR]