The assembly of hard spheres as a structure model of amorphous iron

Abstract

Six assemblies of equal sized hard spheres have been constructed in a manner which is a modification of Bennett's global method, and packing fractions, W ( r ) and I&) of the assemblies have been calculated. Some of the W ( r ) and I,(s) have subpeaks or shoulders on the outer side of the second peaks, which are characteristic of many amorphous transition metals and their alloys. A geometrical origin of the occurrence of the subpeak or shoulder in W ( r ) is briefly discussed. W ( r ) und I,(a) der Anordnungen berechnet. Einige der W ( r ) und I&) haben Submaxima oder Schultern auf der Flanke des zweiten Maximums, die fiir viele amorphe Ubergangsmetalle und ihre Legierungen charakteristisch sind. Ein geometrischer Ursprung fur das Auftreten dieses Submaximurns oder der Schulter in W ( r ) wird diskutiert. Sechs Anordnungen von harten Kugeln gleicher GroDe werden mit der modifizierten Bennett-Methode konstruiert und die Packungsanteile

On the origin of second-peak splitting in the static structure factor of metallic glasses

“…Even if the final result (a 3D model arrangement of like atoms) would be virtually the same as that obtained by DRPHS model building [12], quench simulation by molecular dynamics [15] or sequential atom addition to a selected seed [5,13,16], the DRPSU approach allows a more transparent description, in which different aspects (network topology, interconnection mode, structural unit) can be distinguished and treated separately. Moreover, other properties are easily recognized without the need to perform statistical analyses; thus, it is immediately clear that the structure is homogeneous, virtually isotropic and built from tetrahedra whose distortions (inherent to frustration [17], the impossibility to tile flat space with tetrahedra) are evenly distributed.…”

Structure of Ni-B-Melts by Means of X-Ray Diffraction

“…The normalized atomic distances for molten and amorphous nickel-boron and iron-boron alloys as well as for a tetrahedral model [8] [5] this behaviour is explained by a higher degree of imperfection of the tetrahedral atomic arrangement in the molten state than in the amorphous state (compare [6] and [7] [5], and amorphous Fe 80 B 20 [5]. We can also see from the values of Table 2 These weighting factors show that the interatomic distances reported in Table 2 mainly represent Ni-Ni distances.…”

“…In the case of amorphous alloys this asymmetry normally occurs as shoulder or as subpeak. As shown in [6] and [7], by means of dense random hard sphere packing models, the weakening of the shoulder on the second maximum of the structure factor of the melt can be explained by a smearing out of the tetrahedral atomic arrangement of the amorphous alloy. For melts up to now a similar behaviour was only observed in two cases, namely for the Fe-B-system [5] and for the Mn-Sisystem [3].…”

Multi-center electronic structure calculations for plasma equation of state

“…To construct our ensemble of random ion positions [ 91 ], we employed the algorithm of [ 92 , 93 ] to generate random packings of equal sized [ 94 ] as well as poly disperse hard spheres [ 95 ]. A molecular dynamics based algorithm of [ 96 , 97 ] was employed as well and found equally effective.…”