Surface energy of M2AC(0001) determined by density functional theory (M=Ti,V,Cr; A=Al,Ga,Ge)

Mušić, Denis; Sun, Zhimei; Ahuja, Rajeev; Schneider, Jochen M.

doi:10.1016/j.susc.2006.11.025

Cited by 27 publications

(15 citation statements)

References 46 publications

(72 reference statements)

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“…Both Cr d – C p and Cr d – Al p hybridized states shift to higher energies, which suggests bond weakening, while the Cr d – Cr d states are less affected. These observations are consistent with literature 10 , 11 .…”

Section: Resultssupporting

confidence: 94%

“…Cr 2 AlC has been reported to exhibit self-healing behaviour 8, 9 . A large number of theoretical predictions on MAX phase materials has been published, being focused on the calculation of energetics 10, 11 , electronic structure 10 , thermal properties 12, 13 , growth phenomena 2 , tribological 2 , mechanical 12–14 , and magnetic properties 15 . Furthermore, defects in MAX phases have been studied, including point-defects induced by intrinsic impurities 16 , which imply antisite and interstitial incorporation 8, 9 , as well as extrinsic impurities, such as O, which can be relevant for self-healing applications 17 .…”

Section: Introductionmentioning

confidence: 99%

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Nanometre-scale 3D defects in Cr2AlC thin films

Chen

Mušić

Shang

et al. 2017

Sci Rep

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MAX-phase Cr2AlC containing thin films were synthesized by magnetron sputtering in an industrial system. Nanometre-scale 3D defects are observed near the boundary between regions of Cr2AlC and of the disordered solid solution (CrAl)xCy. Shrinkage of the Cr-Cr interplanar distance and elongation of the Cr-Al distance in the vicinity of the defects are detected using transmission electron microscopy. The here observed deformation surrounding the defects was described using density functional theory by comparing the DOS of bulk Cr2AlC with the DOS of a strained and unstrained Cr2AlC(0001) surface. From the partial density of states analysis, it can be learned that Cr-C bonds are stronger than Cr-Al bonds in bulk Cr2AlC. Upon Cr2AlC(0001) surface formation, both bonds are weakened. While the Cr-C bonds recover their bulk strength as Cr2AlC(0001) is strained, the Cr-Al bonds experience only a partial recovery, still being weaker than their bulk counterparts. Hence, the strain induced bond strengthening in Cr2AlC(0001) is larger for Cr d – C p bonds than for Cr d – Al p bonds. The here observed changes in bonding due to the formation of a strained surface are consistent with the experimentally observed elongation of the Cr-Al distance in the vicinity of nm-scale 3D defects in Cr2AlC thin films.

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Section: Resultssupporting

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Nanometre-scale 3D defects in Cr2AlC thin films

Chen

Mušić

Shang

et al. 2017

Sci Rep

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“…Music et al [ 13 , 14 ] then studied other 211 MAX phases including Ti 2 AlC, confirming that the A-group termination was the most stable (001) surface. However, Music et al [ 13 , 14 ] did not distinguish between surfaces for which it is possible to have different elements in the subsurface layer. For Ti 2 AlC, they only reported the surface energy with Ti on the surface, but did not mention whether Al or C was in the subsurface layer.…”

Section: Introductionmentioning

confidence: 94%

“…Since a catalyst support material would have surfaces present on a particle, the most stable surfaces were investigated. Other studies have investigated the (001) surfaces of some MAX phases [12][13][14][15][16][17]; however, there is little consistency in the literature.…”

Section: Introductionmentioning

confidence: 99%

DFT Study of MAX Phase Surfaces for Electrocatalyst Support Materials in Hydrogen Fuel Cells

et al. 2020

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In moving towards a greener global energy supply, hydrogen fuel cells are expected to play an increasingly significant role. New catalyst support materials are being sought with increased durability. MAX phases show promise as support materials due to their unique properties. The layered structure gives rise to various potential (001) surfaces. DFT is used to determine the most stable (001) surface terminations of Ti2AlC, Ti3AlC2 and Ti3SiC2. The electrical resistivities calculated using BoltzTraP2 show good agreement with the experimental values, with resistivities of 0.460 µΩ m for Ti2AlC, 0.370 µΩ m for Ti3AlC2 and 0.268 µΩ m for Ti3SiC2. Surfaces with Al or Si at the surface and the corresponding Ti surface show the lowest cleavage energy of the different (001) surfaces. MAX phases could therefore be used as electrocatalyst support materials, with Ti3SiC2 showing the greatest potential.

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“…By now, the valence electron structure (VES) can be either calculated by first principle [10] or by empirical electron theory (EET) [11], but for the solid solution, the first principle is not commonly used since the structure type is very limited [12]. On the other side, the EET developed by Yu et al [13] is much simpler and more observable, which is widely used in the materials science [14].…”

Section: Introductionmentioning

confidence: 99%

Effect of the La addition content on valence electron structure and properties of ZrB2 ceramics

Wang

Qing

et al. 2010

Front. Mater. Sci. China

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ZrB 2 is a combined bonding compound composed of strong covalent bonds which make it difficult to sinter and densify. Thus, rare earth or other metal elements are usually used to be sintering additives to improve its sintering properties. To forecast properties of ZrB 2 solid solutions with addition of lanthanum, their valence electron structure (VES) was calculated by using the empirical electron theory (EET) of solids and molecules, and the effect of lanthanum with various proportion on the VES and properties of ZrB 2 ceramics has been studied. The results show that with the increase of the lanthanum addition content, the hybridization steps of Zr and B atoms of ZrB 2 solid solutions are still A16 and 5, respectively. The hybridization step of lanthanum is always A1. The covalent electron numbers and bonding energy of the strongest bonds of the ZrB 2 matrix decrease with the lanthanum addition content increase. These suggest that the addition of lanthanum will improve the fracture toughness and decrease the hardness, crystal cohesive energy and melting point of ZrB 2 . In a word, its sintering properties are improved, and its densities are increased.

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Surface energy of M2AC(0001) determined by density functional theory (M=Ti,V,Cr; A=Al,Ga,Ge)

Cited by 27 publications

References 46 publications

Nanometre-scale 3D defects in Cr2AlC thin films

Nanometre-scale 3D defects in Cr2AlC thin films

DFT Study of MAX Phase Surfaces for Electrocatalyst Support Materials in Hydrogen Fuel Cells

Effect of the La addition content on valence electron structure and properties of ZrB2 ceramics

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