| 1. |
- Ding, Haoming, et al.
(författare)
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Progress in Structural Tailoring and Properties of Ternary Layered Ceramics
- 2023
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Ingår i: Journal of Inorganic Materials. - : SCIENCE PRESS. - 1000-324X. ; 38:8, s. 845-884
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Forskningsöversikt (refereegranskat)abstract
- MAX/MAB phases are a series of non-van der Waals ternary layered ceramic materials with a hexagonal structure, rich in elemental composition and crystal structure, and embody physical properties of both ceramics and metals. They exhibit great potential for applications in extreme environments such as high temperature, strong corrosion, and irradiation. In recent years, two-dimensional (2D) materials derived from the MAX/MAB phase (MXene and MBene) have attracted enormous interest in the fields of materials physics and materials chemistry and become a new 2D van der Waals material after graphene and transition metal dichalcogenides. Therefore, structural modulation of MAX/MAB phase materials is essential for understanding the intrinsic properties of this broad class of layered ceramics and for investigating the functional properties of their derived structures. In this paper, we summarize new developments in MAX/MAB phases in recent years in terms of structural modulation, theoretical calculation, and fundamental application research and provide an outlook on the key challenges and prospects for the future development of these layered materials.
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| 2. |
- Hallstedt, Bengt, et al.
(författare)
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Thermodynamic evaluation of the Al-Cr-C system
- 2006
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Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:5, s. 539-542
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Tidskriftsartikel (refereegranskat)abstract
- The system Al-Cr-C contains one ternary phase, Cr2AlC. By combining a Calphad assessment with ab initio calculations and differential thermal analysis, the Gibbs energy of Cr2AlC could be determined and the complete phase diagram calculated. Cr2AIC melts incongruently at about 1773 K to form Cr7C3 (or Cr3C2) and Al4C3 in addition to liquid. According to the ab initio calculations the equilibrium composition of Cr2AIC is very nearly stoichiometric, but can dissolve some Al metastably by replacing Cr. The agreement between the thermodynamic calculation and the various sources of information is excellent.
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| 3. |
- Liao, Jiamin, et al.
(författare)
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Design of High-Efficiency Visible-Light Photocatalysts for Water Splitting : MoS2/AlN(GaN) Heterostructures
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:31, s. 17594-17599
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen fuel produced from water splitting using solar energy and a catalyst is a clean and renewable future energy source. Great efforts in searching for photocatalysts that are highly efficient, inexpensive, and capable of harvesting sunlight have been made for the last decade, which, however, have not yet been achieved in a single material system so far. Here, we predict that MoS2/AlN(GaN) van der Waals (vdW) heterostructures are sufficiently efficient photocatalysts for water splitting under visible-light irradiation based on ab initio calculations. Contrary to other investigated photocatalysts, MoS2/AlN(GaN) vdW heterostructures can separately produce hydrogen and oxygen at the opposite surfaces, where the photoexcited electrons transfer from AlN(GaN) to MoS2 during the photocatalysis process. Meanwhile, these vdW heterostructures exhibit significantly improved photocatalytic properties under visible-light irradiation by the calculated optical absorption spectra. Our findings pave a new way to facilitate the design of photocatalysts for water splitting.
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| 4. |
- Miao, Naihua, et al.
(författare)
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First-principles investigation on the phase stability and chemical bonding of mInSb.nInTe phase-change random alloys
- 2010
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 150:29-30, s. 1375-1377
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Tidskriftsartikel (refereegranskat)abstract
- The phase stability and bond character of mInSb.nInTe (m = 1, n = 2 or 3) phase-change materials have been investigated by means of ab initio calculations. The results show that In3SbTe2 (IST312) is a metastable phase and is less stable than In4Sb1Te3 (IST413). IST312 will decompose into InSb and InTe as analyzed by formation energies. The chemical bonding in IST312 is rather inhomogeneous, i.e. strong and weak In-Sb or In-Te bonded pairs observed in IST312, which is similar to the available phase-change materials and may lead to its easy phase-change. While in IST413, the bond strengths of In-Sb or In-Te are identical. The present results will provide a fundamental understanding on the phase stability and chemical bonding of mInSb.nInTe (m = 1, n = 2 or 3) alloys and may be applied to develop new InSbTe based phase-change materials.
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| 5. |
- Miao, Naihua, et al.
(författare)
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Investigation on Ge5-x Sb (x) Te-5 phase-change materials by first-principles method
- 2010
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 99:4, s. 961-964
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Tidskriftsartikel (refereegranskat)abstract
- The structure stability and chemical bonding of Ge5-x Sb (x) Te-5 (x=0,1,2) phase-change alloys were studied by ab initio calculations. By analyzing formation energies, density of states and electron localization function, we have shown that the chemical bonding character of Ge4Sb1Te5 is quite similar to that of GeTe and hence a NaCl crystalline state is expected. The introduction of extra electrons by Sb in Ge4Sb1Te5 and Ge3Sb2Te5 results in states at the Fermi Level. With increasing Sb contents as in Ge3Sb2Te5, the chemical bonding becomes rather inhomogeneous.
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| 6. |
- Miao, Naihua, et al.
(författare)
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Mechanical properties and electronic structure of the incompressible rhenium carbides and nitrides : A first-principles study
- 2011
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 151:23, s. 1842-1845
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Tidskriftsartikel (refereegranskat)abstract
- By means of first-principles calculations, the structural stability, mechanical properties and electronic structure of the newly synthesized incompressible Re(2)C, Re(2)N, Re(3)N and an analogous compound Re(3)C have been investigated. Our results agree well with the available experimental and theoretical data. The proposed Re(3)C is shown to be energetically, mechanically and dynamically stable and also incompressible. Furthermore, it is suggested that the incompressibility of these compounds is originated from the strong covalent bonding character with the hybridization of 5d orbital of Re and the 2p orbital of C or N, and a zigzag topology of interconnected bonds, e.g., Re-Re, Re-C or Re-N bonding.
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| 7. |
- Music, Denis, et al.
(författare)
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Electronic structure and shearing in nanolaminated ternary carbides
- 2006
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 139:4, s. 139-143
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Tidskriftsartikel (refereegranskat)abstract
- We have studied shearing in M2AlC phases (M = Sc, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) using ab initio calculations. We propose that these phases can be classified into two groups based on the valence electron concentration induced changes in C-44. One group comprises M = VB and VIB, where the C-44 values are approximately 170 GPa and independent of the corresponding MC. The other group includes M = IIIB and IVB, where the C-44 shows a linear dependency with the corresponding MC. This may be understood based on the electronic structure: shear resistant bands are filled in M2AlC phases with M = VB and VIB, while they are not completely filled when M = IIIB and IVB. This notion is also consistent with our stress-strain analysis. These valence electron concentration induced changes in shear behaviour were compared to previously published valence electron concentration induced changes in compression behaviour [Z. Sun, D. Music, R. Ahuja, S. Li, J.M. Schneider, Phys. Rev. B 70 (2004) 092102]. These classification proposals exhibit identical critical valence electron concentration values for the group boundary. However, the physical mechanisms are not identical: the classification proposal, for the bulk modulus is based on MC-A coupling, while shearing is based on MC-MC coupling.
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| 8. |
- Music, D., et al.
(författare)
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Surface energy of M(2)AC(0001) determined by density functional theory (M = Ti, V, Cr; A = Al, Ga, Ge)
- 2007
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 601:4, s. 896-899
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the correlation between the valence electron configuration and the electronic structure of M(2)AC(0001) surfaces (M = Ti, V, Cr; A = Al, Ga, Ge) by density functional theory. The A surface termination is the most stable configuration for all systems studied according to our surface energy data. As the M valence electron population is increased, the surface energy increases by 22% and 12% for A = Al and Ga, respectively, while it decreases by 29% for A = Ge. This can be understood by evaluating the valence electron concentration induced changes in the surface density of states. Antibonding surface Md-Ap states are present as Ti is substituted by Cr in M(2)AC(0001) for A = Al and Ga, while antibonding surface Md-Ap states are not present as Ti is substituted by Cr in M2GeC(0001).
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| 9. |
- Sa, Baisheng, et al.
(författare)
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Ab initio study of the structure and chemical bonding of stable Ge3Sb2Te6
- 2010
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 12:7, s. 1585-1588
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Tidskriftsartikel (refereegranskat)abstract
- The atomic arrangements and chemical bonding of stable Ge3Sb2Te6, a phase-change material, have been investigated by means of ab initio total energy calculations. The results show that an ordered stacking of Ge-Te-Ge-Te-Sb-Te-Te-Sb-Te-Ge-Te- is the most stable configuration in respect that the -Sb-Te-Te-Sb- configuration enhances the structure stability as analyzed by electron localization function (ELF) and bond energies. Ge3Sb2Te6 shows the character of a p-type semiconductor as seen from the density of states. The chemical bonding of Ge3Sb2Te6 is rather inhomogeneous; strong and weak covalence coexist between Te and Sb atoms, while the strength of the covalent bonding between Te and Ge atoms of various Te-Ge bonds is very close, whereas the interaction between the neighboring Te layers is a van der Waals-type weak bond. The bonding character of Ge3Sb2Te6 is assumed to be applied to the other pseudobinary nGeTe center dot mSb(2)Te(3) phase-change materials.
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| 10. |
- Sa, Baisheng, et al.
(författare)
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First-principles investigations of electronic and mechanical properties for stable Ge2Sb2Te5 with van der Waals corrections
- 2014
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 82, s. 66-69
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Tidskriftsartikel (refereegranskat)abstract
- The Te-Te weak van der Waals-type bonding plays an important role in Ge2Sb2Te5, a widely investigated phase-change material and a potential topological insulator. In this work, we have studied the electronic and mechanical properties of stable Ge2Sb2Te5 using ab initio calculations with the van der Waals corrections. The results show that the van der Waals corrections combined with hybrid functions improve the descriptions of the electronic structure of stable Ge2Sb2Te5. The band gap of similar to 0.5 eV in very good agreement with the experimental value for stable Ge2Sb2Te5 has been successfully reproduced. Furthermore, we have predicted the elastic constants and mechanical properties of stable trigonal Ge2Sb2Te5.
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