Temperature-controlled tunable acoustic metamaterial with active band gap and negative bulk modulus

In this work, the elastic anisotropy, mechanical stability, and electronic properties for P42/mnm XN (XN = BN, AlN, GaN, and InN) and Pbca XN are researched based on density functional theory. Here, the XN in the P42/mnm and Pbca phases have a mechanic stability and dynamic stability. Compared with the Pnma phase and Pm-3n phase, the P42/mnm and Pbca phases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (B), shear modulus (G), and Poisson’s ratio (v) of XN in the P42/mnm and Pbca phases are smaller than those for Pnma XN and Pm-3n XN, and larger than those for c-XN, indicating that Pnma XN and Pm-3n XN are more ductile than P42/mnm XN and Pbca XN, and that c-XN is more brittle than P42/mnm XN and Pbca XN. In addition, in the Pbca phases, XN can be considered a semiconductor material, while in the P42/mnm phase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in the P42/mnm and Pbca phases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.

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General band gap condition in one-dimensional resonator-based acoustic metamaterial

Physics Letters A ◽

10.1016/j.physleta.2016.01.012 ◽

2016 ◽

Vol 380 (9-10) ◽

pp. 1082-1086 ◽

Cited By ~ 1

Author(s):

Yafei Liu ◽

Zhilin Hou ◽

Xiujun Fu

Keyword(s):

Band Gap ◽

One Dimensional ◽

Acoustic Metamaterial

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Band Gaps in a Multiresonator Acoustic Metamaterial

Journal of Vibration and Acoustics ◽

10.1115/1.4000784 ◽

2010 ◽

Vol 132 (3) ◽

Cited By ~ 160

Author(s):

G. L. Huang ◽

C. T. Sun

Keyword(s):

Band Gap ◽

Continuum Model ◽

Lattice System ◽

Band Gaps ◽

Equivalent System ◽

Mass System ◽

Acoustic Metamaterial ◽

Single Mass ◽

Band Gap Structure ◽

Gap Structure

In this study, we investigated dispersion curves and the band gap structure of a multiresonator mass-in-mass lattice system. The unit cell of the lattice system consists of three separate masses connected by linear springs. It was demonstrated that the band gaps can be shifted by varying the spring constant and the magnitude of the internal masses. By using the conventional monatomic (single mass) lattice model as an equivalent system, the effective mass was found to become negative for frequencies in the band gaps. An attempt was made to represent the two-resonator mass-in-mass lattice with a microstructure continuum model. It was found that the microstructure continuum model can capture the dispersive behavior and band gap structure of the original two-resonator mass-in-mass system.

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First Principles Study on the Structural, Elastic, Electronic and Optical Properties of Cubic ‘Half-Heusler’ Alloy RuVAs Under Pressure

International Journal of Material and Mathematical Sciences ◽

10.34104/ijmms.020.051063 ◽

2020 ◽

pp. 51-63 ◽

Cited By ~ 1

Keyword(s):

Optical Properties ◽

Band Structure ◽

Bulk Modulus ◽

Band Gap ◽

Elastic Constants ◽

First Principles ◽

Theoretical Data ◽

Lattice Parameter ◽

Electronic Band ◽

Electronic And Optical Properties

The pressure effect (0 to 40 GPa) on the structural, elastic, electronic, and optical properties of half-metallic compound RuVAs has been investigated employing the DFT based on the first-principles method. The CASTEP computer code is used for this investigation. The calculated lattice parameter show slide deviation from the synthesized and other theoretical data. The normalized lattice parameter and volume are decreased with increasing pressure. The zero pressure elastic constants and also the pressure-dependent elastic constants are positive up to 40 GPa and satisfy the Born stability condition which ensured that the compound RuVAs is stable in nature. At zero pressure, the electronic band gap of 0.159 eV is observed from the band structure calculations which ensured the semimetallic nature of RuVAs. No band gap is observed in the electronic band structure at 40 GPa which indicates the occurrence of phase transition of compound RuVAs at this pressure. We have calculated the value of bulk modulus B, shear modulus G, Young’s modulus E, Pugh ratio B/G, Poisson’s ratio ν and anisotropy factor A of this compound by using the Voigt-Reuss-Hill (VRH) averaging scheme under pressure. The bulk modulus shows a linear response to pressure so that the hardness of this material is increased with increasing pressure. Furthermore, the optical properties such as reflectivity, absorptivity, conductivity, dielectric constant, refractive index, and loss function of RuVAs were evaluated and discussed under pressure up to 40 GPa.

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Role of electronegativity on the bulk modulus, magnetic moment and band gap of Co2MnAl based Heusler alloys

Journal of Science Advanced Materials and Devices ◽

10.1016/j.jsamd.2019.02.001 ◽

2019 ◽

Vol 4 (1) ◽

pp. 158-162

Author(s):

Author-Shiv Om Kumar ◽

Vineeta Shukla ◽

Sanjeev Kumar Srivastava

Keyword(s):

Bulk Modulus ◽

Band Gap ◽

Magnetic Moment ◽

Heusler Alloys

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The Effect of Lanthanum Doping and Oxygen Vacancy on Perovskite, Pyrochlore Oxide and Lanthanide Titanates: A First Principle Study

MRS Advances ◽

10.1557/adv.2019.41 ◽

2019 ◽

Vol 4 (20) ◽

pp. 1167-1175

Author(s):

Amar Deep Pathak ◽

Foram Thakkar ◽

Suchismita Sanyal ◽

Arian Nijmeijer ◽

Hans Geerlings

Keyword(s):

Bulk Modulus ◽

Band Gap ◽

Density Functional ◽

Electronic Conductivity ◽

Formation Enthalpy ◽

Wide Band ◽

Layered Perovskite ◽

Lanthanum Doping ◽

Reducing Environment ◽

La Substitution

AbstractThe effects of La-substitution into SrTiO3 (STO) perovskite oxides on their phase structure, formation enthalpy and electrical conductivity have been investigated. La substitution in STO has been reported to show a significant enhancement in electronic conductivity in a wide-band-gap layered perovskite compound STO. Mixture of Lanthanum and Titanium oxide may lead to various phases including La2/3TiO3, La2Ti2O7 and La2TiO5. In this work, more than 50 structural models have been constructed by considering ionic state substituents, distance between substituents and their concentrations. We investigated the formation enthalpy, elastic properties and band gap by density functional theory (DFT) calculations. We have also investigated the effect of reducing environment on La2/3TiO3. The computed bulk modulus (∼2.4 % deviation) and band gap (∼12% deviation) of STO are in good agreement with the literature. Our results indicate that La substitution into STO could significantly reduce the band gap. Reduction in band gap is maximum when the substituents is present at low concentrations. Internal position of La substituents in STO affects the band gap marginally while energy remains almost same. Formation enthalpy of La2/3TiO3 from LaTiO3 is around 2 eV. La2/3TiO3 acts as band insulator (band gap = 2.8 eV). In reducing environment, the band gap of La2/3TiO3 significantly reduces. Sr substitution in La2/3TiO3 lower the band gap and formation enthalpy. La2Ti2O7 and La2TiO5 have higher band gap and lower bulk modulus than STO. Sr substitution is not feasible in La2Ti2O7 and La2TiO5.

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Ab initio Electronic Band Structure Calculations for Beryllium Chalcogenides

International Journal of Modern Physics B ◽

10.1142/s0217979298001149 ◽

1998 ◽

Vol 12 (19) ◽

pp. 1975-1984 ◽

Cited By ~ 43

Author(s):

G. Kalpana ◽

G. Pari ◽

A. Mookerjee ◽

A. K. Bhattacharyya

Keyword(s):

Bulk Modulus ◽

Band Gap ◽

Structural Transition ◽

Electronic Band Structure ◽

Local Density ◽

Structural Phase ◽

Experimental Results ◽

Orbital Method ◽

Electronic Band ◽

Indirect Band Gap

The first principles tight-binding linear muffin-tin orbital method within the local density approximation (LDA) has been used to calculate the ground state properties structural phase transition and pressure dependence of the band gap of BeS, BeSe and BeTe. We have calculated the energy-volume relations for these compounds in the B3 and B8 phases. The calculated lattice parameters, bulk modulus and the pressure-volume relation were found to be in good agreement with the recent experimental results. We have also calculated the cohesive energy for them and they are consistent with the bulk modulus. The calculated B3 to B8 structural transition pressure for BeS, BeS and BeTe agree well with the experimental results. Our calculations show that these compounds are indirect band gap (Γ-X) semiconductors at ambient conditions. The calculated band gap values are found to be underestimated by 20–30% which is due to the usage of LDA. After the structural transition to the B8 phase BeS continues to be indirect band gap semiconductor and ultimately it becomes metallic above 100 GPa. BeSe and BeTe are metallic at B3 to B8 structural transition.

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