Silicate glasses of the composition (Li2O)x(SiO2)100−x (x= 0, 20, 33.3, and 40) have been prepared and characterized by X‐ray and neutron diffraction experiments using the technique of isotopic substitution. Thus, at each composition, a set of independent diffraction patterns allows the discussion of the short‐range and medium‐range structure. For the short‐range structure, average coordination numbers and atomic‐pair distances are obtained from the pairdistribution functions. For the medium‐range structure, i.e., for atomic‐pair distances >0.5 nm, an increase of the amplitudes of the oscillations in the pair‐distribution function is observed with increases in the Li2O content.
The aim of the present paper is to state differences in the spatial distribution of valency electrons for free metal atoms and for molten metals. The element lithium was chosen since both its inner and outer electrons play an important role, so that when a precise X-ray and a precise neutron-diffraction experiment have been carried out a difference, if it exists at all. should be recognizable. The correction of the X-ray data for inelastic, i.e. Compton scattering was done on the basis of an inelastic measurement performed on a spectrometer equipped with a position sensitive detector.
The structure factors S (q) calculated from the X-ray and neutron diffraction data show very good coincidence within the whole q-range. Slight deviations for 0 ≦ q ≦ 1.7 Å-1 are discussed but yield no hint at all on electron correlations independent of the nuclei.
The structure factors of the molten elements Si and Ge were determined by means of neutron diffraction. Together with the structure factors of molten Sn and Pb, taken from literature, specific variations in the run of the curves can be detected. Especially, a shoulder on the larger g-side of the main maximum becomes larger going from Pb to Si. A model is given which describes these melts as being composed of hard spheres and tetrahedra. The concentration of tetrahedra is evaluated
The three partial Faber Ziman structure factors as well as the Bhatia Thornton structure factors of the metallic glass NigiBig were evaluated by neutron diffraction experiments using the isotopic substitution method. In one of the investigated specimens the isotopic composition of the components was adjusted in such a way as to make it possible to measure directly with one diffraction experiment the correlation between the metalloid atoms. From the three partial pair correlation functions the atomic distances and the partial coordination numbers are determined. The results demonstrate the strong chemical ordering in amorphous NisiBig. Particularly the distance correlation between the boron atoms turned out to be very pronounced.The experimental results agree with the main features of a geometrical packing model of soft spheres.
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