Size versus electronic factors in transition metal Laves phase stability

Abstract

The different roles played by atomic size and electronic factors in stabilizing the transition metal Laves phases against the two competing phases C11b(MoSi2) and C16(CuAl2) are studied within a simple tight binding d bond model. Good qualitative agreement with the experimental AB2 structure map is found if size and electronic factors are both included.

The Influence of the Valence Electron Concentration on the Structural Variation of the Laves Phases MgNi2–xGex

“…The three primary Laves phase structure types are MgCu 2 , MgZn 2 , and MgNi 2 , which are denoted according to the Strukturbericht symbols with C15, C14, and C36, respectively. The three-dimensional networks of the smaller atoms B are built by vertexand face-sharing tetrahedral B 4 . In MgCu 2 and MgZn 2 the centers of gravity of these B 4 tetrahedra as well as the Mg atoms themselves are arranged like the carbon atoms in the cubic and hexagonal diamond structure, respectively.…”

Mg1–yScyZn2: Limited Sc/Mg Alloying between Laves Phase MgZn2 and ScZn2 – What Drives ScZn2 into a High‐Pressure Phase?

“…[12] The stability of Laves phases has been mainly considered in view of two major concepts: the geometrical [20][21][22] and electronic rules. [23] The geometric rule, based on close packing of different sized atoms, generalizes that Laves phases form under the condition r A /r B = 1.15-1.30, with an ideal value of 1.225. The electronic factor of the stability of Laves phases has been discussed in terms of valence electron concentration (VEC), electronegativity, and chemical bonding, and so on.…”

Crystal-Structure Analysis with Moments of the Density-of-States: Application to Intermetallic Topologically Close-Packed Phases

“…The dominant factors that govern their structural stability are the average number of valence electrons [1][2][3][4] and differences in atomic size [5,6]. This has been investigated in detail for the χ phase [7], the Laves phases [8][9][10], the A15 phase [11][12][13][14], and the σ phase [15]. The theoretical analysis of TCP phases is mostly based on density-functional theory (DFT) calculations [16][17][18][19][20][21][22][23][24][25] and approximate electronic structure methods [12,13,[26][27][28][29].…”