The crystal structure of this compound has been determined by Patterson and Fourier syntheses and refined by Fo-Fc syntheses. Each copper atom is surrounded by four oxygen atoms of four different formate ions in an approximately square configuration and by two water molecules at a greater distance. The formate ion is nearly symmetrical with an O-C-O angle of 120 ° .In the course of our investigations on paramagnetic resonance absorption, it became desirable to know the atomic arrangements of the crystals of cupric formate tetra-and di-hydrates. The present note reports the structure analysis of the former carried out by us recently. Kabraji (1931) has already given the cell dimensions, the number of formula units and the space group.Useful X-ray data in the present experiments were obtained from oscillation photographs taken with Cu K~ radiation (4 = 1.542/~): The unit cell, containing two formula units, has the dimensions a = 8-18±0-02, b = 8.15±0.02, c = 6.35±0.02 J~, = 101 ° 5'±20', which almost agree with Kabraji's data, the morphological value of fl being taken. From the systematic absences, the space group was found to be P2i/a-C~h (not C2z/m-C~h as reported by Kabraji); The intensities of the reflexions were estimated visually and corrected for Lorentz and polarization factors. In view of the small size of the crystals used, absorption and extinction corrections were neglected. Because the general point position in P2z/a is fourfold, and since the unit cell contains only two formula units, it follows that the copper atoms must occupy special positions.From the ordinary Patterson maps projected along three crystallographic axes, approximate parameters for the O~, On, ~ and Ozv atoms could be determined, while those for the C atoms remained less certain. Next, the electron-density maps projected along the c and b axes were prepared by taking into account probable positions of the C atoms. The atomic parameters were refined by two-dimensional Fourier syntheses and structure-factor calculations Table 2.* The R factors are 0.10, 0.12 and 0.11 for (h/c0), (hO1) and (Ok/), respectively, when the absent and over-exposed spectra are excluded.
The electrical conductivity and magnetic susceptibility of binary compounds CuxSe (x=2.0, 1.8, 1.5, 1.0 and 0.5) and CuxS (x=1.8 and 1.0) were studied over the temperature range from -150°C to 150°C. These compounds are near metallic conductors with resistivities of 100 to 6000µΩ·cm. It is found that Cu3Se2 may be antiferromagnetic, while the others are diamagnetic or weakly paramagnetic. A qualitative discussion is presented on the basis of the valencies of constituents and coordination configurations in order to explain the physical properties of these substances.
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