Crystal Structures, Stabilities, Electronic Properties, and Hardness of MoB<sub>2</sub>: First-Principles Calculations

Ding, Liping; Shao, Peng; Zhang, Fanghui; Lü, Cheng; Ding, Li; Ning, Shuya; Huang, Xiao

doi:10.1021/acs.inorgchem.6b00899

Cited by 45 publications

(27 citation statements)

References 63 publications

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“…Prior to the phonon calculations, the crystal structure was relaxed until the residual force on each atom was less than 0.001 eV Å−1 . The relaxed lattice parameters are in good agreement with experimental result [25][26][27]. To compute the surface states, we first calculate the second-order rank tensor of force constants in Cartesian coordinates based on DFPT, from which we obtain the tight-binding parameters for the bulk and surface atoms.…”

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confidence: 72%

Phononic Helical Nodal Lines with PT Protection in MoB2

et al. 2019

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While condensed matter systems host both Fermionic and Bosonic quasi-particles, reliably predicting and empirically verifying topological states is only mature for Fermionic electronic structures, leaving topological Bosonic excitations sporadically explored. This is unfortunate, as Bosonic systems such a phonons offer the opportunity to assess spinless band structures where nodal lines can be realized without invoking special additional symetries to protect against spin-orbit coupling.Here we combine first-principles calculations and meV-resolution inelastic x-ray scattering to demonstrate the first realization of parity-time reversal (PT ) symmetry protected helical nodal lines in the phonon spectrum of MoB2. This structure is unique to phononic systems as the spin-orbit coupling present in electronic systems tends to lift the degeneracy away from high-symmetry locations. Our study establishes a protocol to accurately identify topological Bosonic excitations, opening a new route to explore exotic topological states in crystalline materials.

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confidence: 72%

Phononic Helical Nodal Lines with PT Protection in MoB2

et al. 2019

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“…The expression is written as follows where v b is the volume of the bond, which can be given by v b μ = ( d μ ) 3 /∑[( d v ) 3 N b v ], P is the Mulliken population, and f m is a factor of metallicity . This method has been successfully used to evaluate the transition-metal carbides and borides. − …”

Section: Results and Discussionmentioning

confidence: 99%

Prediction of Molybdenum Nitride from First-Principle Calculations: Crystal Structures, Electronic Properties, and Hardness

et al. 2018

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Transition metal (TM) nitrides has been widely used in many scientific and technical areas because of their unique physical and mechanical properties. However, most of the well-known transition metal nitrides are nitrogen deficient. The reports on nitrogen-rich TM nitrides are rather scarce and sometimes even show discrepancy in their crystal structures. Herein, the microstructure, stability, electronic property, and hardness of nitrogen-rich molybdenum nitride MoN2 compound have been investigated systematically by using an unbiased structure search method crystal structure analysis by particle swarm optimization combined with first-principle calculations. Our study demonstrates a stable configuration orthorhombic Cmc21 (no. 36) for MoN2 crystal, which is even lower in energy than the experimental synthesized structure rhombohedral R 3 m -MoN2 at ambient pressure condition. The formation enthalpies with respect to the reactant Mo + N2, mechanical stabilities, and phonon dispersions further confirm the stability of Cmc21-MoN2 phase at the whole ambient condition, indicating that it can be synthesized in experiment. According to the density of states, it is seen that all the considered MoN2 exhibit metallic behavior and have two types of bonds (covalent and ionic). The Vicker hardness of Cmc21-MoN2 is calculated as 11.987 GPa, and the strength and number of covalent bonds may dominate its hardness.

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“…It provides reliable predictions of the ground state and metastable structures of the known stable compositions of SnS, SnS 2 , and Sn 2 S 3 . Many higher-energy metastable structures are also predicted that are yet to be experimentally verified, but may be feasible under high temperature or high-pressure growth conditions. ,− An important finding is the mixed-valent Sn 3 S 4 composition that appears as a marginally stable phase. Its occurrence has been alluded to, but not definitively observed in previous studies.…”

Section: Discussionmentioning

confidence: 99%

Computational Design of Mixed-Valence Tin Sulfides as Solar Absorbers

Wang

Liu

Zhao

et al. 2019

ACS Appl. Mater. Interfaces

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Binary tin sulfides, such as SnS and SnS2, are appealing because of their simple stoichiometry and semiconducting properties and are, therefore, being pursued as potentially cost-effective materials for optoelectronic applications. The multivalency of Sn, that is, Sn(+2) and Sn(+4) allows yet more intermediate compositions, SnxSy, whose structures and properties are of interest. Sn2S3 is already under consideration as a mixed-valence semiconductor. Other intermediate compositions, for example, Sn3S4 and Sn4S5 have remained elusive, although their existences have been alluded to in literature. Here we report a comprehensive study of phase stability of the SnxSy series compounds, utilizing swarm-intelligence crystal structure search method combined with first-principles energetic calculations. We find that the stability of mixed-valence SnxSy compounds with respect to decomposition into pure-valence SnS and SnS2 is in general weaker than the SnxOy counterparts, likely due to differences in chemical bonding. Besides identifying the experimentally discovered stable phases of Sn2S3, our calculations indicate that the Sn3S4 phase is another mixed-valence composition which shows marginal stability with respect to decomposition into SnS and SnS2. Other studied compositions may be metastable under ambient conditions, with slightly positive formation enthalpies. We find two structures of Sn3S4 having comparably low 2 energies, both of which feature one-dimensional chain-like fragments obtained by breaking up the edge-connected octahedral layers of SnS2. Both structures indicate lattice phonon stability and one shows quasi-direct band gap with a calculated value of 1.43 eV, ideal for solar absorbers. A further analysis of the composition-structureproperty relationship supports the notion that lowdimensional Sn-S motifs and van der Waals interaction may lead to diverse structure types and chemical compositions, having functional properties that are yet to be identified in the SnxSy series with mixed valency.conditions, SnS (Pnma; herzenbergite) is the known ground state, having a band gap of about 1 eV, 11,16−19 close to the optimum photon absorption threshold. At elevated temperature or pressure there are at least four known polymorphs that include orthorhombic (Cmcm) and cubic (zincblende, rocksalt, π-cubic) structures. 18,20−27 On the other end, SnS2 is a layered two-dimensional (2D) semiconductor, which exhibits different polytypic stacking sequence depending upon growth temperature. 28,29 Its band gap, reported around 2 eV, 6,11,30−32 is large compared to SnS (Pnma). An intermediate compound, Sn2S3, has recently attracted attention because it features both +2 and +4 30

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Crystal Structures, Stabilities, Electronic Properties, and Hardness of MoB₂: First-Principles Calculations

Cited by 45 publications

References 63 publications

Phononic Helical Nodal Lines with PT Protection in MoB2

Phononic Helical Nodal Lines with PT Protection in MoB2

Prediction of Molybdenum Nitride from First-Principle Calculations: Crystal Structures, Electronic Properties, and Hardness

Computational Design of Mixed-Valence Tin Sulfides as Solar Absorbers

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Crystal Structures, Stabilities, Electronic Properties, and Hardness of MoB2: First-Principles Calculations

Cited by 45 publications

References 63 publications

Phononic Helical Nodal Lines with PT Protection in MoB2

Phononic Helical Nodal Lines with PT Protection in MoB2

Prediction of Molybdenum Nitride from First-Principle Calculations: Crystal Structures, Electronic Properties, and Hardness

Computational Design of Mixed-Valence Tin Sulfides as Solar Absorbers

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Crystal Structures, Stabilities, Electronic Properties, and Hardness of MoB₂: First-Principles Calculations