Neutron Diffraction Study of Liquid As-Se and As-Te Systems
The neutron diffraction measurement in liquid As<I><SUB>x</SUB></I>Se<SUB>1−<I>x</I></SUB> and As<I><SUB>x</SUB></I>Te<SUB>1−<I>x</I></SUB> alloys with <I>x</I>=0.20∼0.571 has been carried out to analyze the local atomic arrangement in these liquid alloys. The first sharp diffraction peak (FSDP) of the structure factor, <I>S</I>(<I>Q</I>), in the liquid As–Se alloys was observed at all <I>x</I>, indicating that existing structural units are partially connected as in the amorphous state, while, the FSDP in the liquid As–Te alloys almost disappears, particularly, in the Te rich composition range. The first peak of atomic pair distribution function, <I>g</I>(<I>r</I>), in the liquid As–Se alloys is well-resolved, reflecting the strong As–Se covalent bondings. On the other hand, the first peak of <I>g</I>(<I>r</I>) in the liquid As–Te alloys is broadened and its position largely shifts with <I>x</I>. Results by the least square analysis for diffraction intensities have been summarized as follows: The connecting AsSe<SUB>3⁄2</SUB> pyramidal unit, which is the basic structural element at As<SUB>2</SUB>Se<SUB>3</SUB>, is formed over a wide composition range in the As–Se alloys but bondings between like atoms such as Se–Se and As–As are present only in the limited composition range. On the other hand, in the liquid As–Te alloys both As–As and Te–Te bondings, in addition to the As–Te one, can be observed at all <I>x</I> containing As<SUB>2</SUB>Te<SUB>3</SUB>. The results have also pointed out that the metallic property of the liquid As–Te alloys is attributable to the change of the bonding nature relating to Te on melting.
- Materials transactions, JIM
Materials transactions, JIM 39(11), 1135-1139, 1998-11