Structure and stability of Laves phases. Part I. Critical assessment of factors controlling Laves phase stability

Stein, Frank; Palm, Martin; Sauthoff, Gerhard

doi:10.1016/j.intermet.2004.02.010

Cited by 358 publications

(211 citation statements)

References 125 publications

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“…In particular, we used canonical nearest-neighbour bond integrals [21] ddσ : ddπ : ddδ = −6 : 4 : −1 (6) with a decay ∝ 1/R 5 and band-widths as obtained from tight-binding calculations. The second moment µ (2) was chosen identical for all structures to guarantee that the structural energy differences are to first order given by the differences in bonding energy [8].…”

Section: Structural Trendsmentioning

confidence: 99%

“…Ref. [6]) indicate that the structural stability of the Laves phases is governed by atomic size and packing ratio. In contrast, the electronic structure plays an important role in the stabilization of A15 and σ at the structural transitions from hcp to bcc at a d-band filling of N ≈ 3 and from bcc to hcp at a half-full d-band (N ≈ 5).…”

Section: Structural Trendsmentioning

confidence: 99%

“…Ref. [6] for a recent review on Laves phases). In many cases such effects can be identified in structure maps that are based on a one-dimensional ordering parameter for the elements, the so-called Mendeleev number M [7,8] (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Topologically Close-Packed Phases in Superalloys: Valence-Dependent Bond-Order Potentials Based on Ab-Initio Calculations

Hammerschmidt¹,

Seiser²,

Drautz³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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Refractory elements are used in Ni-based superalloys to increase creep resistance (Mo, Re, W) and to retard the coarsening of the γ' phase (Re). At high concentrations of refractory elements precipitation of topologically closepacked (tcp) phases [1] is detrimental to the creep properties of the alloys. A more detailed understanding of the formation kinetics and thermodynamic stability of tcp phases will therefore be beneficial for the design of the next generation superalloys. Atomistic modeling of tcp stability with interatomic potentials requires to go beyond the second-moment approximation to the electronic density of states by including up to at least the sixth moment [2]. We have developed an analytic bond-order potential (BOP) that systematically takes into account higher moment contributions to the density of states and depends explicitly on the valence of the transition-metal elements [3]. For the parameterization of the new BOP, we performed extensive density functional theory (DFT) calculations of elemental and binary compound phases of Ni, the technologically important alloying element Cr, and the refractory metals Mo, Re, and W. We will discuss the structural trends of the DFT calculations, compare to the predictions of the analytic BOP and report on our progress on the parameterization of the analytic BOP for the Re-W system. This work is part of the EPSRC-funded collaborative multi-scale project 'Alloys by Design'.

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Section: Structural Trendsmentioning

confidence: 99%

Section: Structural Trendsmentioning

confidence: 99%

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Modeling Topologically Close-Packed Phases in Superalloys: Valence-Dependent Bond-Order Potentials Based on Ab-Initio Calculations

Hammerschmidt¹,

Seiser²,

Drautz³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Hammerschmidt¹,

Ladines²,

Koßmann³

et al. 2016

Crystals

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Abstract:The moments of the electronic density-of-states provide a robust and transparent means for the characterization of crystal structures. Using d-valent canonical tight-binding, we compute the moments of the crystal structures of topologically close-packed (TCP) phases as obtained from density-functional theory (DFT) calculations. We apply the moments to establish a measure for the difference between two crystal structures and to characterize volume changes and internal relaxations. The second moment provides access to volume variations of the unit cell and of the atomic coordination polyhedra. Higher moments reveal changes in the longer-ranged coordination shells due to internal relaxations. Normalization of the higher moments leads to constant (A15,C15) or very similar (χ, C14, C36, µ, and σ) higher moments of the DFT-relaxed TCP phases across the 4d and 5d transition-metal series. The identification and analysis of internal relaxations is demonstrated for atomic-size differences in the V-Ta system and for different magnetic orderings in the C14-Fe 2 Nb Laves phase.

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“…A break-through in the targeted development of materials with superior properties based on intermetallics compared to steel alloys can only be expected after a much better understanding of their stability and chemical bonding [5]. First-principles density functional theory calculations have been broadly used to study the electronic structure and mechanical properties of laves phase compound.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of structural and electronic properties of Laves phases structures YM₂(M = Cu and Zn)

Benabadji¹,

Faraoun²

2013

MATEC Web of Conferences

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Abstract. First-principles calculations have been carried out to investigate the structural properties and electronic structure of the main binary Laves phase YCu 2 and YZn 2 with C14, C14, C36 and CeCu 2 structures in Cu-Y-Zn alloy, respectively. The total energies of Laves phases with various occupations of nonequivalent lattice sites in all four structural forms have been calculated Ab initio by a pseudopotential VASP code. The optimized structural parameters were in very good agreement with the experimental values. The calculated heat of formation showed that the CeCu 2 -YCu 2 and YZn 2 Laves phase was of the strongest alloying ability and structural stability. The electronic density of states (DOS) and charge density distribution were given.

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Structure and stability of Laves phases. Part I. Critical assessment of factors controlling Laves phase stability

Cited by 358 publications

References 125 publications

Modeling Topologically Close-Packed Phases in Superalloys: Valence-Dependent Bond-Order Potentials Based on Ab-Initio Calculations

Modeling Topologically Close-Packed Phases in Superalloys: Valence-Dependent Bond-Order Potentials Based on Ab-Initio Calculations

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

First-principles study of structural and electronic properties of Laves phases structures YM₂(M = Cu and Zn)

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Structure and stability of Laves phases. Part I. Critical assessment of factors controlling Laves phase stability

Cited by 358 publications

References 125 publications

Modeling Topologically Close-Packed Phases in Superalloys: Valence-Dependent Bond-Order Potentials Based on Ab-Initio Calculations

Modeling Topologically Close-Packed Phases in Superalloys: Valence-Dependent Bond-Order Potentials Based on Ab-Initio Calculations

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

First-principles study of structural and electronic properties of Laves phases structures YM2(M = Cu and Zn)

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First-principles study of structural and electronic properties of Laves phases structures YM₂(M = Cu and Zn)