Explaining stability of transition metal carbides – and why TcC does not exist

Wang, Qinggao; German, K.; Oganov, Artem R.; Dong, Huafeng; Feya, Oleg D.; Zubavichus, Ya. V.; Murzin, Vadim

doi:10.1039/c5ra24656c

Cited by 40 publications

(21 citation statements)

References 41 publications

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“…Each filled circle data point represents the formation enthalpy of a single relaxed structure. One immediate observation is that metal-rich compositions ( x < 0.5 in Co 1– x C x ) are generally lower in energy than carbon-rich phases, consistent with the observation that compounds with a low carbon concentration are generally favored among the mid-to-late transition metals . This search found the Pnnm -Co 2 C (Fe 2 C-type) structure as the lowest energy compound, with a formation enthalpy of 0.065 eV.…”

Section: Resultssupporting

confidence: 68%

“…Hägg rationalized the crystal structures observed in TMCs on the basis of the relative atomic ratio, r = r C / r M , with r = 0.59 being the cutoff where carbon atoms are no longer able to fit neatly into the interstitial sites of the metal lattice . This is the main justification for why interstitial compounds are not observed beyond group VI elements, , with more complex structuresusually metal-richbeing formed instead. One example is iron cementite, Fe 3 C, which is the predominant carbide in the Fe–C system .…”

Section: Introductionmentioning

confidence: 99%

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High-Pressure Synthesis of Bulk Cobalt Cementite, Co₃C

et al. 2021

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Transition metal carbides find use in a wide range of advanced high-resilience applications including high-strength steels, heat shields, and deep-earth drills. However, carbides of the mid-to-late transition metals remain difficult to isolate and characterize on account of their metastability, which precludes the preparation of high-quality bulk single crystal samples using traditional solid-state methods. Herein, we report a combined computational and experimental survey of the cobalt–carbon binary system under high pressures and demonstrate that pressure offers a route toward the bulk synthesis of the metastable cementite-type cobalt carbide, Co3C, which under ambient conditions can only be prepared in low-dimensional thin film or nanoparticle forms. First-principles calculations reveal two competitive low-energy stoichiometric phases under ambient pressuresPnnm-Co2C (Fe2C-type) and Pnma-Co3C (Fe3C-type)consistent with the known low-dimensional phases that have been studied for their promising magnetic properties. However, the calculated formation enthalpy of Pnma-Co3C decreases steadily with the applied pressure, while that of Pnnm-Co2C increases. We pursue these results using high-pressure laser-heated synthesis methods coupled with in situ X-ray diffraction and observe the formation of Pnma-Co3C above 4.8 GPa. We determine the experimental bulk modulus of Co3C to be K 0 = 237 GPa (K p = 4.0). First-principles calculations of the phonon modes in Co3C reveal dynamical instabilities at ambient pressure that are absent under compression. These results offer a promising new route for the synthesis of rare-earth-free magnets.

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Section: Resultssupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

High-Pressure Synthesis of Bulk Cobalt Cementite, Co₃C

et al. 2021

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“…TM–C bonds are weakened with the increasing filling of the d-band. This applies to all parent TMs: 3d, 4d, and 5d [ 37 , 45 ]. Thus, the tendency of the metallic character of TMCs increases from left to right and from top to bottom in groups IVB–VIB of the periodic table.…”

Section: Resultsmentioning

confidence: 99%

Comparative Analysis of the Phase Interaction in Plasma Surfaced NiBSi Overlays with IVB and VIB Transition Metal Carbides

Bober

Senkara

2021

Materials

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Important applications of transition metal carbides (TMCs) are as wear resistant composite layers deposited by plasma transferred arc welding (PTAW) and laser methods. Growing interest in them has also been observed in additive manufacturing and in HEA technology (bulk composite materials and layers), and in the area of energy conversion and storage. This paper presents the results of comparative studies on interfacial interactions in the NiBSi−TMCs system for two border IVB and VIB TM groups of the periodic table. Model (wettability and spreadability) and application experiments (testing of the PTAW-obtained carbide particle−matrix boundaries) were performed. Fe from partially melted steel substrates is active in the liquid NiBSi−TMCs system. It was revealed that the interaction of TMCs with the liquid NiBSi matrix tends to increase with the group number, and from the top to bottom inside individual groups. Particles of IVB TMCs are decomposed by penetration of the liquid along the grain boundaries, whereas those of VIB are decomposed by solubility in the matrix and secondary crystallization. No transition zones formed at the interfacial boundaries of the matrix−IVB group TMCs, unlike in the case of the VIB group. The experimental results are discussed using the data on the TMC electronic structure and the physicochemical properties.

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“…The evolutionary algorithm for structure prediction, as implemented in the USPEX code [36,37], has succeed in predicting many hereto unknown carbides [38][39][40][41][42][43][44]. Using the USPEX code, we firstly performed variable-composition structure searches with up to 33 atoms in a unit cell for the V-C system at zero temperature and zero pressure.…”

Section: Methodsmentioning

confidence: 99%

Discovering novel VC1− compounds through hybrid first-principles and evolutionary algorithms

Xie

Liu

Cheng

et al. 2016

Journal of the European Ceramic Society

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Explaining stability of transition metal carbides – and why TcC does not exist

Abstract: A simple understanding on the trend of stability for transition metal carbides.

Cited by 40 publications

References 41 publications

High-Pressure Synthesis of Bulk Cobalt Cementite, Co₃C

High-Pressure Synthesis of Bulk Cobalt Cementite, Co₃C

Comparative Analysis of the Phase Interaction in Plasma Surfaced NiBSi Overlays with IVB and VIB Transition Metal Carbides

Discovering novel VC1− compounds through hybrid first-principles and evolutionary algorithms

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Explaining stability of transition metal carbides – and why TcC does not exist

Abstract: A simple understanding on the trend of stability for transition metal carbides.

Cited by 40 publications

References 41 publications

High-Pressure Synthesis of Bulk Cobalt Cementite, Co3C

High-Pressure Synthesis of Bulk Cobalt Cementite, Co3C

Comparative Analysis of the Phase Interaction in Plasma Surfaced NiBSi Overlays with IVB and VIB Transition Metal Carbides

Discovering novel VC1− compounds through hybrid first-principles and evolutionary algorithms

Contact Info

Product

Resources

About

High-Pressure Synthesis of Bulk Cobalt Cementite, Co₃C

High-Pressure Synthesis of Bulk Cobalt Cementite, Co₃C