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Structural study of liquid eutectic Ag-Ge alloy has been performed at 1123K by means of neutron diffraction. The experiments were carried out using the 'concentration method' and the isotopic substitution method. The pair partial correlation functions, the partial nearest-neighbour numbers and the distances d1 between Ag-Ag, Ge-Ge and Ag-Ge pairs are given. Predominant Ag-Ge interactions are explained in a way that is consistent with the thermodynamic properties.

The structure factors of liquid Cerium and Praseodymium have been determined at 1 100 C by neutron diffraction. For theoretical and experimental reasons paramagnetic scattering has been assumed to be identical in both liquid and solid states. The pair correlation functions, neighbour distances and coordination number were then obtained by Fourier transform. The structure factor S(k) exhibits an anomalous behaviour compared with simple metallic ions.

In this paper we present a study of local order in amorphous and liquid SeTe systems. The first part is a neutron scattering study of the Selenium in the amorphous state at room temperature and in the liquid state from the melting point up to 900 C. The Se 1−x Te x mixtures are studied in the amorphous state up to 40% atomic Tellurium and in the liquid state up to 100% Tellurium. The pair correlation function clearly emphasizes the importance of the covalent bonding the divalence of the Selenium and the very sharp 1st and 2nd peaks even at high temperatures and up to 50% Tellurium. Hence in the second part we deal with a quasi-crystalline model already used for the liquid Selenium up to 900 C. A generalization of this calculation to binary systems provides us with a fair simulation of amorphous and liquid Se 1−x Te x systems structure factors. For the lowest concentrations in Tellurium the short range order seems to be mainly substitutional, as far as the Selenium chains are concerned. By increasing the Tellurium concentration the 3-valency of Tellurium in the liquid state produces a chain branching which distorts the Selenium-like structure.

On rappelle les principaux travaux concernant les proprietes structurales du gallium liquide obtenues par diffraction des rayonnements dans l'intervalle de temperature compris entre 163 K et 1 303 K. Le comportement en fonction de la temperature du facteur de structure presente certains desaccords avec les previsions de la theorie de Schneider sur la limite de stabilite des liquides en surfusion. L'interpretation des donnees structurales montre qu'il y a une similitude entre l'ordre a courte distance dans le liquide et celui de la forme cristalline metastable β. Cette analogie et l'etude du potentiel interatomique conduisent a infirmer l'existence de liaisons courtes covalentes dans le liquide.

A structure study of the liquid Pd0.825Si0.175 alloy has been performed by X-ray and neutron diffraction. As the contribution of the Si pairs to the scattered intensity is very small, the partial interference functions have been evaluated for the Pd-Pd and Pd-Si atomic pairs and compared with those obtained from a hard sphere model. The partial interference function JPd-Pd is very similar to that deduced from the Percus-Yevick calculation but the agreement is not as good for the Pd-Si pairs. This may be due to the fact that the chosen model only takes into account the size effect between the particles and does not include their chemical interaction.

2014 Structural studies of liquid Ag at 1 323 K and liquid Ag-Ge alloys at 1 123 K have been carried out by means of neutron diffraction. The pair correlation functions were evaluated by means of a Fourier transform and coordination numbers were calculated. The interference functions are compared with those deduced from Percus-Yevick calculation. Using the assumption of concentration independency, partial interference functions are evaluated for Ag-Ag and Ge-Ge pairs. They are shown to be very similar to the respective structure factors of liquid silver and liquid germanium. LE JOURNAL DE PHYSIQUE TOME 37, DECEMBRE 1976, Classification Physics Abstracts 7.126

The electrical resistivity for liquid Ga between 303K and 573K is calculated from the Ziman formula, using structure factors which have been measured with a great accuracy and various pseudopotentials. It is shown that two forms of pseudopotentials provide the authors with a fair agreement between the calculated resistivity and the experimental one measured by Pokorny and Astrom (1976). The part played by the effective mass and the empty-core radius is outlined in a discussion.

Many recent developments have occurred in the study of the local structure of liquid tellerium, and the generally admitted picture for that structure has changed considerably in the last few years. Until recently, liquid tellerium was believed to be made of helicoidal chains of tellerium atoms, in the same way as liquid sulphur and liquid selenium. Consequently, it had to be a reasonably good (or, at least, not to too bad) liquid semiconductor. The first troubles came when various experiments showed that liquid tellerium was a metal and not a semiconductor 1−4 ). Then, the first neutron elastic scattering experiments, conducted by Tourand and Breuil in Saclay 5 ), showed that a covalent network was nevertheless preserved. Cabane and Friedel 6 ) attempted to reconcile these apparently contradictory behaviours in a model where the chain structure is progressively replaced by a three-dimensional network of covalent bonds. More systematic experiments were made in Saclay 7 ) at the same time; they gave further support to the idea of a three dimensional network, and allowed a rather precise description of the corresponding local structure. This paper summarizes what we know in the present status of the experiments; further details can be found in refs. 6 and 7.

Les systèmes désordonnés amorphes ont commencé à susciter l'intérêt des Physiciens et des Chimistes bien avant la découverte de leurs propriétés de commutation d'un état semiconducteur à un état métallique. La caractéristique essentielle de ces matériaux est bien évidemment la non-périodicité à longue distance pour des systèmes à l'état solide. D'un point de vue phénoménologique, un amorphe était défini comme un corps ne présentant pas de spectre de diffraction fin. Nous tenterons de définir de façon plus rigoureuse cet état amorphe puis, dans le cadre des propriétés structurales, dont la connaissance est essentielle pour une meilleure compréhension de ces systèmes, nous rappellerons comment est définie la fonction de distribution de paire g(r). Nous montrerons quelles sont les informations que cette fonction permet d'obtenir pour la connaissance de l'ordre local, et quelles sont les limites de son utilisation en fonction des approximations utilisées. Nous examinerons ensuite brièvement les différentes méthodes d'investigation dont nous disposons pour obtenir cette fonction de corrélation de paire. Nous insisterons alors plus particulièrement sur le cas des neutrons thermiques en montrant la démarche suivie pour obtenir à partir de l'information expérimentale (intensité diffusée) la fonction de corrélation de paire g(r) que nous utilisons comme paramètre d'étude de l'ordre à courte distance.

Neutron scattering measurements on liquid gallium have been carried out at 293, 838 and 1 303 K on the H10 spectrometer of the EL3 reactor at Saclay. The obtained structure factors and pair correlation functions are compared to various published data. A quasi-crystalline model related to the β monoclinic form of gallium is proposed in order to explain the shape of the structure factor of liquid gallium and its behaviour versus temperature.

In this paper we present a study of the short range order and of the coordination number in liquid Selenium-Tellurium systems.

The structure factor of liquid tellurium has been measured by neutron diffraction at the melting temperature and in the supercooled state. These results are a confirmation of the existence of an A7 type stable configuration in a large range of temperature between 400 and 1100°C.

The structure factor of liquid lanthanum has been measured by neutron diffraction, and turns out to be strongly different from other liquid metals structure factors obtained hitherto.

La structure du tellure liquide a ete determinee par diffraction de neutrons, a onze temperatures differentes, comprises entre 575 °C et 1 725 °C. On a obtenu par transformation de Fourier, la fonction de distribution de paire g(r) et calcule le nombre de coordinance pour chacune de ces temperatures. Ces experiences mettent en evidence, une transformation progressive en fonction de T, de la configuration du tellure en phase liquide.