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The complex chalcogenides with excellent memory switching properties are mainly situated close to the border of glass formation domain. The simulation of the structural changes occurring during the memory switching process of a ternary chalcogenide composition has been carried out. The transition of a high resistivity Ge[As.sub.4][Te.sub.7] amorphous cluster with 120 atoms to a low resistivity crystalline cluster was analyzed. The coordination of atoms changes from that corresponding to 8-N coordination rule (two for tellurium, three for arsenic, and four for germanium) in the amorphous phase to six (the same for all atoms) in metastable crystalline phase. Because of spatial constraints exercised by the amorphous matrix, the amorphous cluster cannot expand. In these circumstances Te atoms seem to be over-coordinated (up to sixfold-coordinated). During the switching process, the atoms are moving on distances up to 4.0 Å. The average displacement is of 2.36 Å. PACS Nos.: 47.20.Hw, 77.84.Bw, 78.55.Qr, 77.80.Fm, 83.10.Tv. Les complexes chalcogenures avec d'excellentes proprietes de commutation de resistance a memoire se situent maintenant pres de la frontiere de la formation de verre. Nous faisons ici une simulation des changements structuraux qui se produisent lors de la commutation de memoire d'un compose chalcogenure tertiaire. Nous analysons la transition entre l'amas de 120 atomes de haute resistance de a-Ge[As.sub.4][Te.sub.7], vers l'amas cristallin de basse resistance. La coordinence des atomes change, de celle correspondant a un indice de coordination 8-N (deux pour le Te, trois pour l'As et quatre pour le Ge) dans la phase amorphe, a six (la meme pour tous les atomes) dans la phase cristalline metastable. A cause des contraintes spatiales exercees par la matrice amorphe, l'amas amorphe ne peut pas s'etendre. Dans ces circonstances, l'indice de coordination des atomes de Te est tres eleve (jusqu'il six fois). Pendant le processus de commutation, les atomes se deplacent sur des distances allant jusqu'il 4.0 Å. Le deplacement moyen est de 2.36 Å. [Traduit par la Redaction], 1. Introduction The complex chalcogenides with memory switching properties (phase change materials) are the core of the nonvolatile solid-state memory devices or phase change random access memory. The knowledge of [...]

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The complex chalcogenides with excellent memory switching properties are mainly situated close to the border of glass formation domain. The simulation of the structural changes occurring during the memory switching process of a ternary chalcogenide composition has been carried out. The transition of a high resistivity GeAs4Te7 amorphous cluster with 120 atoms to a low resistivity crystalline cluster was analyzed. The coordination of atoms changes from that corresponding to 8-N coordination rule (two for tellurium, three for arsenic, and four for germanium) in the amorphous phase to six (the same for all atoms) in metastable crystalline phase. Because of spatial constraints exercised by the amorphous matrix, the amorphous cluster cannot expand. In these circumstances Te atoms seem to be over-coordinated (up to sixfold-coordinated). During the switching process, the atoms are moving on distances up to 4.0 Å. The average displacement is of 2.36 Å. [ABSTRACT FROM AUTHOR]