Fundamental Study of the Structural Analysis of Monoatomic Liquids by X-ray Diffraction

This report presents an experimental procedure in X-ray diffraction study to determine the atomic distribution in monoatomic liquids. The methods for the corrections, normalization and the Fourier analysis on the X-ray scattering intensity from liquid sample (liquid mercury at 15℃) have been discussed in detail. The main results are as follows : 1) The atomic scattering factor should be modified by an anomalous dispersion effect. 2) Krogh-Moe-Morman\u27s method is a useful one for the normalization of the X-ray scattering intensity. 3) When the different divergence-slits are used to measure the X-ray scattering intensity, the ratio of intensity obtained deviate from the value given from the ratio of the divergence ; namely this ratio is a function of the scattering angle. Hence, this factor should be considered on the analysis within the experimental error

Structural Investigation of Amorphous and Quasicrystalline Al-based Alloys by the Anomalous X-ray Scattering (AXS) Method

An attempt has been made in this paper to present the current information about the atomic structures of both amorphous and icosahedral Al_Cu_V_ alloys and icosahedral Al_Cu_Fe_ alloy determined by the anomalous x-ray scattering (AXS) method as well as the ordinary x-ray diffraction. Characteristic features of their intensity profiles are observed, and the structural parameters of coordination numbers and interatomic distances determined from the RDF analysis clearly indicate the presence of the icosahedral short-range ordering clusters in the as-quenched amorphous sample and other annealed amorphous samples, which are similar to the fundamental atomic distribution constructing the icosahedral phase. The AXS measurements at the Cu and Fe K-absorption edges also provide the possible interpretation about the distribution of these components in the icosahedral short-range ordering clusters

The Structure of Liquid Hg-Na and Hg-K Alloys

The X-ray scattering intensity of liquid Hg-Na and Hg-K alloys have been measured along their liquidus temperatures. The change in the total structure factors by alloying is small up to 70 at. % of alkali metals in both systems, although the category of compound forming has been frequently discussed in these liquid alloys. The partial structure factors of these alloys were also obtained assuming that each partial structure is independent of concentration at their liqudius temperatures. The partial structure factor of mercury atom pairs in both alloy systems showed the deviation from that of pure liquid mercury, i. e., the profile of the partial structure factor was more like that of the hard sphere fluids

Structural Study of Cu/Co Multilayer by Anomalous Small-Angle X-ray Scattering

The diffraction peaks in the small-angle region due to a long period of a Cu/Co multilayer were observed with the anomalous small-angle x-ray scattering in reflection geometry. These peaks appear to be enhanced because of a large negative value of the real part of the anomalous. dispersion term of Co just below the Co K-absorption edge. By comparing the relative integrated intensities of these peaks with the theoretical values calculated from a trapezoidal concentration model, the concentration profile along the surface normal in this multilayer has been determined

Apparatus for X-ray Diffraction of Liquid Metals and Several Results

A high temperature attachment for X-ray diffraction of liquid metals has been built enabling liquid metal sample to be measured at temperatures up to 1000℃ in vacuum, whilst scanning angles from 0 to 130°of 2θ. The usefulness of this apparatus was demonstrated by obtaining the structure factors of liquid Al, Pb, Sn, and Bi at several temperatures from the measured X-ray intensities and a comparison was made with those found in earlier works. Numerical values of the structure factors obtained in this work were illustrated

Direct Estimation of Valence Electron Distribution Around an Ion in Liquid Metals

Liquid metals consist of ions and electrons. However, the bare ions in liquid metals are recognized to be partially screened by electrons so as to produce the effective ion-ion potential of the long-range oscillatory type and then liquid metals are likely the binary mixtures of ions with some electrons for partial screening and the valence electrons giving a strongly coupled plasma. An attempt is made in this paper to present the valence electron distribution around an ion in liquid metals. The principle of a new method for estimating such information in liquid metals from measured structural data has been described with some selected examples

Thermodynamic properties and phase equilibria for Pt-Rh alloys

The activity of rhodium in solid Pt-Rh alloys is measured in the temperature range from 900 to 1300 K using the solid-state cell Pt-Rh, Rh + Rh2O3/(Y2O3)ZrO2/Pt1-xRhx + Rh2O3, Pt-Rh The activity of platinum and the free energy, enthalpy, and entropy of mixing are derived. Activities exhibit moderate negative deviation from Raoult's law. The mixing properties can be represented by a pseudosubregular solution model in which excess entropy has the same type of functional dependence on composition as the enthalpy of mixing, ΔH = XRh (1 - XRh)[-10,970 + 45XRh] J/mol ΔSE = XRh (1- XRh)[-3.80 + 1.55 × 10-2 XRh] J/mol·K The negative enthalpy of mixing obtained in this study is in qualitative agreement with predictions of semiempirical models of Miedema and co-workers and Colinet et al. The results of this study do not support the solid-state miscibility gap suggested in the literature, but are consistent with liquidus data within experimental uncertainty limits

Structural Study of Amorphous Alloys with a Wide Supercooled Liquid Region by the Anomalous X-ray Scattering (AXS) Method

The atomic structures of new kinds of as-quenched La_Al_Ni_ and Zr_Al_Ni_ amorphous alloys exhibiting a wide supercooled liquid region and a high reduced glass transition temperature have been studied with the anomalous x-ray scattering (AXS) method in combination with the ordinary x-ray diffraction. The environmental structures around certain constituent elements in the alloys were determined with the AXS method. The atomic structures of these amorphous alloys annealed in the super-cooled liquid region were also investigated. The systematic structural studies revealed a structural feature common to these amorphous alloys. Namely, the environment around a certain element in the amorphous sample is very different from that in the crystallized sample. Such as, Ni atoms around La atoms in La_Al_Ni_ and Al atoms around Zr atoms in Zr_Al_Ni_. In other words, quite a large change of the environments around a certain element is required for the crystallization, which controls the crystallization in these amorphous alloys. Consequently, This may provide a high thermal stability of these amorphous alloys

A Review of Molecular Dynamics Studies on Silica and Silicate Melts((A)Amorphous Alloys)

Current progress of molecular dynamics (MD) simulation on silicate melts has been summarized for recent 15 years. MD simulation is now recognized as one of the useful techniques for providing the short range orderring structures of the melt expressed by the radial distribution function. The long range orderring structures in the melt, on the other hand, have not fully investigated by MD simulation, and the number distribution of -(Si-O-)_n rings or chains is the unique index for characterizing the network structures of silicates. Transport properties and other atomistic dynamics for silicate melt have not also sufficiently investigated except for ionic diffusivity. For further development of the MD simulation studies, one of the most important subjects may be to prepare more physically reliable interatomic potentials which can be used for various composition of silicates

Structural Study of an Amorphous Liquid-quenched Ni_<80>-P_<20> Alloy

The structure of amorphous Ni_-P_ alloy obtained by rapid quenching from the liquid state has been studied by X-ray diffraction. After calculating the structure factor by means of the common Fourier analysis, the atomic radial distribution function is obtained from which interatomic distance and coordination number were estimated. Comparing the results with those in the liquid state, it is found that the general feature of the structure in the amorphous state is quite similar to that in the liquid state. A brief comment on the partial structures in this alloy is also made