Temperature-induced topological differentiation of the two high-density amorphous ices

• Published in: Europhysics letters Vol. 74; no. 3; pp. 445 - 451
• Main Authors: Saitta, A. M, Strässle, Th, Klotz, S
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.05.2006; EDP Sciences; European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing
• Subjects: 61.43.-j; 61.43.Bn; Condensed Matter; Other; Physics; Disordered solids, Structural modeling: serial-addition models, computer simulation
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/epl/i2006-10016-x

The high-density (HDA) and the very high-density (VHDA) amorphous forms of ice are studied through computer simulations. The structural transformations involve, at different stages of compression, two different subgroups of second-shell neighbors. The interplay between these subgroups is found to be crucial in the mechanism of high-pressure differentiation between HDA and VHDA: in HDA they are more separated and the first subgroup is locked in the anti-tetrahedral, ice-VII-like positions all along the downstroke to ambient pressure. In VHDA the annealing under pressure triggers instead the merging of the two subgroups through a counter-intuitive outward displacement of one subgroup of neighbors, resulting then in a local decrease of the coordination number, a more random-close-packed arrangement and a different equation of state.