Structural, mechanical and electronic properties of 3d transition metal nitrides in cubic zincblende, rocksalt and cesium chloride structures: a first-principles investigation

Liu, Z T Y; Zhou, Xiuquan; Khare, S. V.; Gall, Daniel

doi:10.1088/0953-8984/26/2/025404

Cited by 95 publications

(70 citation statements)

References 77 publications

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“…At a slightly higher alloying of 35% ScN, the wurtzite lattice expands further to 12% larger than AlN, and a single diffraction spot that could be attributed to the rocksalt structure is observed via SAED. The position of the rocksalt diffraction spot shows a rocksalt structure with a volume that is 6% smaller than the volume of ScN [75,76], suggesting aluminum incorporation in the rocksalt structure. At 57% ScN alloying, the wurtzite lattice is essentially unchanged from that observed for the 35% ScN composition; however, a stronger intensity is seen for the rocksalt structure.…”

Section: B Experimentsmentioning

confidence: 95%

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Talley

Millican

Mangum

et al. 2018

Phys. Rev. Materials

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An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system (Al 1−x Sc x N) can highlight opportunities and design principles for enhancing desired material properties by leveraging nonequilibrium states. The fundamental thermodynamics, and therefore composition-and structuredependent mechanisms, underlying property evolution in this system have not been fully described, despite significant recent efforts driven by interest in enhanced piezoelectric performance. Practical realization of these enhanced properties, however, is hindered by the strong driving thermodynamic driving force for phase separation in the system, highlighting the need for increased study into the role of heterostructural alloying on the thermodynamics and composition-structure-property relationships in this system. With this need in mind, ab initio computed alloy thermodynamics and properties are compared to combinatorial thin-film synthesis and characterization to develop a more complete picture of the structure and property evolution across the Al 1−x Sc x N composition space. The combination of structural frustration and a flattened free-energy landscape lead to substantial increases in electromechanical response. The energy scale of alloy metastability is found to be much larger than previously reported, helping to explain difficulties in achieving homogeneous materials with high scandium concentration. Scandium substitution for aluminum softens the wurtzite crystal lattice, and energetic proximity to the competing hexagonal boron-nitride structure enhances the piezoelectric stress coefficient. Overall, this work provides insight into the understanding of the structure-processing-property relationships in the Al 1−x Sc x N system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.

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Section: B Experimentsmentioning

confidence: 95%

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Talley

Millican

Mangum

et al. 2018

Phys. Rev. Materials

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“…During each run, the cell shape, volume, and atomic positions were allowed to freely relax until forces were below 0.01 eV/Å, similar to earlier works [43][44][45][46][47][48] . If this value could not be reached afer more than 100 steps, an energy criterion of 1 meV per atom was used.…”

Section: Experimental and Computational Detailsmentioning

confidence: 99%

Structural transition in the magnetoelectricZnCr2Se4spinel under pressure

et al. 2016

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Τhe magnetoelectric ZnCr 2 Se 4 spinel, with space group Fd3 m, undergoes a reversible first-order structural transition initiating at 17 GPa, as revealed by our highpressure X-ray diffraction studies at room temperature. We tentatively assign the high-pressure modification to a AMo 2 S 4 -type phase, a distorted variant of the monoclinic Cr 3 S 4 structure. Furthermore, our Raman investigation provides evidence for a pressure-induced insulator-metal transition. Our density functional theory calculations successfully reproduce the structural transition. They indicate significant band gap and magnetic moment reduction accompanying the pressure-induced structural modification. We discuss our findings in conjunction with the available high-pressure results on other Cr-based chalcogenide spinels.

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“…The convergence criterion was set to 10 -5 eV in energy during the electronic iterations. For structural optimization, the cell shape and atomic positions were allowed to relax until stress was minimized and force on any atom was below 0.01 eV/Å, similar to earlier works [45][46][47][48][49][50][51] . The pressure dependence was determined by selecting a few volume points covering the equilibrium volumes corresponding to a range of 0 -30 GPa, optimizing the structures at those points and fitting the total energy vs volume to a B-M EoS 36 .…”

Section: Experimental and Computational Detailsmentioning

confidence: 99%

Pressure-induced phase transitions in the CdCr2Se4 spinel

et al. 2016

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We have conducted high-pressure x-ray diffraction and Raman spectroscopic studies on the CdCr 2 Se 4 spinel at room temperature up to 42 GPa. We have resolved three structural transitions up to 42 GPa, i.e. the starting Fd3 m phase transforms at ~11 GPa into a tetragonal I4 1 /amd structure, an orthorhombic distortion was observed at ~15 GPa, whereas structural disorder initiates beyond 25 GPa. Our ab initio DFT studies successfully reproduced the observed crystalline-to-crystalline structural transitions. In addition, our calculations propose an anti-ferromagnetic ordering as a potential magnetic ground state for the high-pressure tetragonal and orthorhombic modifications, as compared to the starting ferromagnetic phase. Furthermore, the computational results indicate that all phases remain insulating in their stability pressure range, with a direct-to-indirect band gap transition for the Fd3 m phase taking place at 5 GPa.We attempted also to offer an explanation behind the peculiar first-order character of the Fd3 m (cubic)→I4 1 /amd (tetragonal) transition observed for several relevant Cr-spinels, i.e. the sizeable volume change at the transition point, which is not expected from space group symmetry considerations. We detected a clear correlation between the cubic-tetragonal transition pressures and the next-nearest-neighbor magnetic exchange interactions for the Crbearing sulphide and selenide members, a strong indication that the cubic-tetragonal transitions in these systems are principally governed by magnetic effects.

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Structural, mechanical and electronic properties of 3d transition metal nitrides in cubic zincblende, rocksalt and cesium chloride structures: a first-principles investigation

Cited by 95 publications

References 77 publications

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Structural transition in the magnetoelectricZnCr2Se4spinel under pressure

Pressure-induced phase transitions in the CdCr2Se4 spinel

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