The Pauling File, Binaries Edition

Villars, P.; Berndt, M.; Brandenburg, Klaus; Cenzual, K.; Daams, J.; Hulliger, F.; Massalski, T. B.; Okamoto, Hiroyuki; Osaki, Kunihiro; Prince, Amber; Putz, Hubert; Iwata, Shuichi

doi:10.1016/j.jallcom.2003.08.058

Cited by 146 publications

(207 citation statements)

References 4 publications

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“…32 The additional prototypes were considered because they are common or related to Mg alloys. 33,34 This protocol gives reasonable results. In Ref.…”

Section: First-principles Methodsmentioning

confidence: 84%

Ordered magnesium-lithium alloys: First-principles predictions

2010

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Magnesium-lithium ͑Mg-Li͒ alloys are among the lightest structural materials. Although considerable work has been done on the Mg-Li system, little is known regarding potential ordered phases. A first and rapid analysis of the system with the high-throughput method reveals an unexpected wealth of potentially stable low-temperature phases. Subsequent cluster expansions constructed for bcc and hcp superstructures extend the analysis and verify our high-throughput results. Of particular interest are those structures with greater than 13 at. % lithium, as they exhibit either partial or complete formation as a cubic structure. Order-disorder transition temperatures are predicted by Monte Carlo simulations to be in the range 200-500 K. I. MOTIVATION AND BACKGROUNDEmerging technologies increasingly depend on the production of ultralight-weight materials. Magnesium-lithium ͑Mg-Li͒ alloys are the lightest metallic alloys, having densities near that of plastics, 1-3 and are strong enough to be used in a variety of high-performance applications. In particular, Mg-Li alloys are good candidates for material applications in industries such as aerospace and automotive manufacturing. 4 As an alloying agent in magnesium, lithium is advantageous principally because of its low density and cubic crystal structure. The addition of lithium converts the hexagonalclose-packed ͑hcp͒ structure of natural magnesium to a more ductile and formable body-centered-cubic ͑bcc͒ alloy. Addition of 13 at. % Li partially converts the alloy to a cubic structure and content exceeding 33 at. % results in total conversion. 5 Although the Mg-Li system has been studied extensively, 5-11 evidence suggesting the formation of ordered phases is notably sparse. Diffusionless transformations of the martensitic type have been observed in pure Li, and similar transformations occur in low-temperature magnesium alloyed lithium at certain concentrations. 11,12 Binary ordered phases have not been conclusively identified, however, and any instances contained in the literature are indeterminate. 6,9,13,14 The results of high-throughput ͑HT͒ ab initio calculations performed with the AFLOW package ͑described later͒ show, however, that the heat of formation is negative for a large number of potential structure types, implying the existence of at least one thermodynamically stable ordered phase ͑Fig. 1͒. II. FIRST-PRINCIPLES METHODFollowing the HT results, we have made predictions of Mg-Li ordered phases using the cluster-expansion ͑CE͒ method-a first-principles-based approach in which input data is mapped to a truncated Ising-type Hamiltonian. The configurational Hamiltonian allows for a fast ground-state search ͑GSS͒ over many derivative superstructures. 16 The CE method was applied to the Mg and Li lattice configurations ͑bcc and hcp, respectively͒. Although minimum-energy configurations may exist outside those considered, superstructures derived from the parent lattices of the alloy constituents generally include the lowest-energy configurations. This assumption is ...

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“…32 The additional prototypes were considered because they are common or related to Mg alloys. 33,34 This protocol gives reasonable results. In Ref.…”

Section: First-principles Methodsmentioning

confidence: 84%

Ordered magnesium-lithium alloys: First-principles predictions

2010

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“…The phase diagrams of the four systems under investigation have been assessed and are reported in the Pauling Files database [15]. Only two stable compounds are reported to exist in the Si-P and Ge-P diagrams, SiP and GeP, whose decomposition occurs at 1160 • C and 750 • C, respectively, via peritectic decomposition into elements P and Si, or Ge.…”

Section: Thermodynamic Considerationsmentioning

confidence: 99%

High-pressure melt growth and transport properties of SiP, SiAs, GeP, and GeAs 2D layered semiconductors

Barreteau

Michon

Besnard

et al. 2016

Journal of Crystal Growth

145

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Silicon and Germanium monopnictides SiP, SiAs, GeP and GeAs form a family of 2D layered semiconductors. We have succeeded in growing bulk single crystals of these compounds by melt-growth under high pressure (0.5-1 GPa) in a cubic anvil hot press. Large (mm-size), shiny, micaceous crystals of GeP, GeAs and SiAs were obtained, and could be exfoliated into 2D flakes. Small and brittle crystals of SiP were yielded by this method. High-pressure sintered polycrystalline SiP and GeAs have also been successfully used as a precursor in the Chemical Vapor Transport growth of these crystals in the presence of I 2 as a transport agent. All compounds are found to crystallize in the expected layered structure and do not undergo any structural transition at low temperature, as shown by Raman spectroscopy down to T=5 K. All materials exhibit a semiconducting behavior. The electrical resistivity of GeP, GeAs and SiAs is found to depend on temperature following a 2D-Variable Range Hopping conduction mechanism. The availability of bulk crystals of these compounds opens new perspectives in the field of 2D semiconducting materials for device applications.

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“…Co can dissolve a relatively large fraction of carbon C and does not form stable ordered carbides, whereas Mo has limited C solubility and forms several stable carbides (even at low temperature). Similarly to Co, Fe can dissolve a relatively large fraction of C (at least in the γ phase), but concomitantly it forms carbides at temperatures relevant to SWCNT growth (Fe 3 C) 35,36 . Nucleation of Fe 3 C and subsequent loss of C solubility 20 can be used to identify the thermodynamic lower limit for the CVD growth of very thin SWCNTs from Fe nanoparticles 22,23 .…”

mentioning

confidence: 99%

Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

et al. 2008

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We explore the role of Mo in Fe:Mo nanocatalyst thermodynamics for low-temperature chemical vapor deposition growth of single walled carbon nanotubes (SWCNTs). By using the size-pressure approximation and ab initio modeling, we prove that for both Fe-rich (∼ 80% Fe or more) and Mo-rich (∼ 50% Mo or more) Fe:Mo clusters, the presence of carbon in the cluster causes nucleation of Mo2C. This enhances the activity of the particle since it releases Fe, which is initially bound in a stable Fe:Mo phase, so that it can catalyze SWCNT growth. Furthermore, the presence of small concentrations of Mo reduce the lower size limit of low-temperature steady-state growth from ∼0.58nmf orpureF eparticlesto ∼ 0.52nm. Our ab initio-thermodynamic modeling explains experimental results and establishes a new direction to search for better catalysts.Critical factors for the efficient growth of single walled carbon nanotubes (SWCNTs) via catalytic chemical vapor deposition (CCVD) 1,2,3 are the compositions of the interacting species (feedstock, catalyst, support 4,5,6,7,8,9,10 ), the preparation of the catalysts, and the synthesis conditions 11,12,13,14,15,16,17,18 . Efficient catalysts must have long active lifetimes (with respect to feedstock dissociation and nanotube growth), high selectivity and be less prone to contamination 19,20,21,22,23 . Common factors that lead to reduction in catalytic activity are deactivation (i.e. chemical poisoning or coating with carbon), thermal sintering (e.g. caused by highly exothermic reactions on the clusters surface 13,14,24 with insufficient heat transfer 25,26 ) and solid-state reactions (nucleation of inactive phases in the cluster 22,23,25 ).Metal alloy catalysts, such as Fe:Co, Co:Mo and Fe:Mo, improve the growth of CNTs 4,10,20,27,28,29,30,31 , because the presence of more than one metal species can significantly enhance the activity of a catalyst 20,32,33,34 , and can prevent catalyst particle aggregation 20,31,32,33 . In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 . This is explained in terms of substantial inter-metallic interaction between Mo, Fe and C 20,35,36 which is congruent with previously observed solid-state reactions between these elements. In fact, the addition of Mo in mechanical alloying of powder Fe and C mixtures 38 promotes solid state reactions even at low Mo concentrations by forming ternary phases, such as the (Fe,Mo) 23 C 6 type carbides 38 .The way in which carbon interacts with transition metals depends on the metal species. Fe and Co belong to the "carbon dissolution-precipitation mechanism" group, where relatively large fractions of carbon dissolve into the cluster before stable carbides are formed, while Mo belongs to the "carbide formation-decomposition" group where carbide formation occurs rapidly at low carbon concentrations 39 . These mechanisms are governed by the interplay between solub...

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The Pauling File, Binaries Edition

Cited by 146 publications

References 4 publications

Ordered magnesium-lithium alloys: First-principles predictions

Ordered magnesium-lithium alloys: First-principles predictions

High-pressure melt growth and transport properties of SiP, SiAs, GeP, and GeAs 2D layered semiconductors

Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

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