Distinctive features of fracture processes in beryllium under impact loading

Characterization of shocked beryllium

“…As the recovery assembly was specifically designed to minimize rarefaction waves from loading the sample to induce tensile failure, a focus of the fractography was to understand how and where nucleation of damage occurred. It is worth noting that no cracks were observed in the plane of the sample as would be expected for sample undergoing a simple spall loading such as reported by Bat'kov [12] and Golubev [13]. In all images the general appearance of the fracture surfaces is consistent with that of cleavage in a characteristically brittle material.…”

Structural mechanism of the formation of mineral Na-tveitite—a new type of phase with a fluorite-derivative structure—in the NaF-CaF2-(Y,Ln)F3 natural system

“…CaF 2 -YF 3 system. In accordance with the struc tural cluster concept of fluorite derivative ordered phases [4][5][6][7][8][9], tveitite Ca 14 Y 5 F 43 belongs to the com pounds described by the crystallochemical formula (14 : 5). The simultaneous presence of clusters for the three afore mentioned compositions may lead to a phase of vari able composition containing from 42 to 44 fluorine anions per formula unit.…”

“…An analysis of the ordered phase structures [4][5][6][7][8][9] indicates that they contain three crystallochemically different types of cations: A (the coordination polyhe dron is a 10 or 14 vertex polyhedron), B (the coordi nation polyhedron is a square antiprism), and C (the coordination polyhedron is a cube, like in the fluorite structure). Fluorine anions are divided into three types: X (located in the octahedral voids of cationic packing to form anionic cuboctahedra), Y (located in the tetrahedral voids of cationic packing to form anionic cubes), and Z (located in the octahedral voids of cationic packing and have anionic cuboctahedral or cubic coordination).…”

“…The purpose of this study was to consider the chemical relationships for two tveitite species (Norve gian and Kola) as phases belonging, respectively, to two and three component systems (CaF 2 -RF 3 and NaF-CaF 2 -RF 3 ) and, based on the structural data on Na tveitite [18] and tveitite [12][13][14] and the proposi tions of the cluster concept for phases with a fluorite derivative structure [4][5][6][7][8][9], analyze their structural relationships in order to establish the structural mech anism of isomorphic sodium incorporation into the basic (tveitite) ordered crystalline matrix.…”

Cluster Theory for Fluorite-like Fluorides Containing Anionic Cuboctahedra

“…This theory describes all the known structure of multicomponent fluoritelike halides oxohalides and oxides, and also allows predicting new structural types, one of which has recently been confirmed by independent studies by other authors. 6,7 has revealed three types of cations and three types of anions in these structures. Cations of A and B sorts are located in transformed coordination polyhedra compared with fluorite, and sort C cations are located in cubes as cations in the structure of the fluorite type.…”