The Packing of Helical and Zigzag Chains and Distribution of Interstitial Voids in Expanded Liquid Se near the Semiconductor to Metal Transition

¹ Department of Chemistry, Faculty of Science, Niigata University, Niigata 50-2181, Japan
² Toyota Technological Institute, Nagoya 468-8511, Japan
³ Department of Physics, Faculty of Science, Kyoto University, Kyoto 606-8224, Japan
⁴ Faculty of Education, Hirosaki University, Hirosaki 036-8560, Japan
⁵ Research Institute for Science Education, Kyoto 603-8346, Japan
⁶ Physikalische Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany

^* e-mail: maruken@sc.niigata-u.ac.jp

Published online: 21 August 2017

Abstract

The reverse Monte Carlo (RMC) and Voronoi-Delaunay (VD) void analyses were applied to study the modification of chain geometries near the semiconductor (SC) to metal (M) transition in expanded liquid Se along the isochore of d = 3.4 g/cm³.

Fluctuations of dihedral angles with increasing temperature and pressure cause modification of the helical (H) chain to the planar zigzag (Z) chain conformations. The distribution of voids size (r_V ) supported by chain segments and distances to the 4th ~ 6th neighbor atoms on the chain segments provide information on the stacking of planar zigzag chains compensated by empty space (L-voids, r_V ~ 3.6 Å) which leads to the formation of metallic domains. Near SC-M transition region the number fraction N_Z/N_H for Z and H chain segments increases.