The local coordination environment at Cu is shown in Figure 1. Two previous applications of HAR to metal hydrates are especially relevant to this work. Encouragingly, some 15 of the citations of the NoSpherA2 method deal primarily with applications, including some of our results. recorded in the Web of Science involve applications of the method, rather than focusing on theory or further method development. Thus, only about 5 of the 168 citations of ref. HAR is now becoming generally recognized as a reliable methodology to improve on IAM refinements, but whilst the concept that “hydrogen atoms can be located accurately and precisely by x-ray crystallography” has been endorsed, the uptake by chemical or mineralogical crystallographers has so far been minimal. HAR is undertaken with the ORCA computational package in conjunction with X-ray structure refinement using olex2.refine, implemented with modern programming languages in an open-source, extensible environment. The method, known as Hirshfeld atom refinement (HAR), has been implemented in the program NoSpherA2, and incorporated into the popular structure determination package Olex2 v.1.5. This approach remains a fully experimental structure determination, using the DFT to calculate custom atomic scattering factors, which are then used to refine the structure in standard applications. įast and accurate density functional theory (DFT) methods now make it entirely feasible to compute accurate, custom, atom scattering factors that directly reflect the electron densities of atoms polarized correctly to the precise location of each atom in a structure. Large single crystals of 3 are of great interest for optical UV filters, and the optical properties of such crystals have been carefully compared to those of aqueous solutions of Ni 2+ salts. ![]() Recent work has demonstrated that this antiferromagnetic character is preserved in nanoparticles of 4. Key interest in the structures of 3 and 4 has been in relation to their antiferromagnetic structures at low temperatures. ![]() Raman spectroscopy has identified librational bands due to H 2O at around 672 cm −1 in eriochalcite, in good agreement with previous work. A novel 2D paramagnetic NMR technique has been applied to powdered CuCl 2∙2D 2O, demonstrating that the paramagnetic shift anisotropy can act as a sensitive probe of distances in paramagnetic solids. ![]() The observed slightly weaker exchange interactions are consistent with the slightly smaller T max and T c in CuCl 2∙2D 2O. The unit cell volume in the deuterated system was found to be about 1.5% larger, implying slightly larger average separations between copper centres. The magnetic properties of 1 have recently been determined and contrasted to those of the deuteride CuCl 2∙2D 2O. The thermal behaviour of 1 has been monitored using Raman scattering spectroscopy, whereby the transition from the orthorhombic dihydrate to the monoclinic anhydrate could be related to the vibrational modes of the two phases. Interest in the paramagnetic chlorides of Cu(II), especially 1 and 2, remains strong.
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