scholarly journals Novel III-V Nitride Polymorphs in the P42/mnm and Pbca Phases

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3743 ◽  
Author(s):  
Qingyang Fan ◽  
Xin Ai ◽  
Junni Zhou ◽  
Xinhai Yu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Band Gap ◽  
Density Functional ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
Wide Band ◽  
Light Emitting ◽  
Ultraviolet Detectors ◽  
Direct Band

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.

scholarly journals Electronic, Mechanical and Elastic Anisotropy Properties of X-Diamondyne (X = Si, Ge)

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3589 ◽  
Author(s):  
Qingyang Fan ◽  
Zhongxing Duan ◽  
Yanxing Song ◽  
Wei Zhang ◽  
Qidong Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Shear Modulus ◽  
Young’S Modulus ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Wide Band ◽  
Band Gaps ◽  
Mechanical Anisotropy ◽  
Semiconductor Materials

The three-dimensional (3D) diamond-like semiconductor materials Si-diamondyne and Ge-diamondyne (also called SiC4 and GeC4) are studied utilizing density functional theory in this work, where the structural, elastic, electronic and mechanical anisotropy properties along with the minimum thermal conductivity are considered. SiC4 and GeC4 are semiconductor materials with direct band gaps and wide band gaps of 5.02 and 5.60 eV, respectively. The Debye temperatures of diamondyne, Si- and Ge-diamondyne are 422, 385 and 242 K, respectively, utilizing the empirical formula of the elastic modulus. Among these, Si-diamondyne has the largest mechanical anisotropy in the shear modulus and Young’s modulus, and Diamond has the smallest mechanical anisotropy in the Young’s modulus and shear modulus. The mechanical anisotropy in the Young’s modulus and shear modulus of Si-diamondyne is more than three times that of diamond as determined by the characterization of the ratio of the maximum value to the minimum value. The minimum thermal conductivity values of Si- and Ge-diamondyne are 0.727 and 0.524 W cm−1 K−1, respectively, and thus, Si- and Ge-diamondyne may be used in the thermoelectric industry.

First Principles Investigation of Electronic Structure, Chemical Bonding, Elastic and Optical Properties of Novel Rhenium Nitrides

2012 ◽  
Vol 512-515 ◽  
pp. 883-889
Author(s):  
Qing Lin Xia ◽  
Liu Xian Pan ◽  
Yuan Dong Peng ◽  
Li Ya Li ◽  
Hong Zhong Wang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Density Of States ◽  
Chemical Bonding ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Hexagonal Phase ◽  
Partial Density

we investigate the electronic structure, chemical bonding, optical and elastic properties of the novel rhenium nitrides, hexagonal phase re3n and re2n by using density-functional theory (dft) within generalized gradient approximation (gga). the calculated equilibrium lattice constants of both re3n and re2n are in reasonable agreement with the experimental results. the band structure along the higher symmetry axes in the Brillouin zone, the density of states (dos) and the partial density of states (pdos) are presented. the calculated energy band structures and dos show that re3n and re2n are metal compounds. The dos and pdos show that the dos at the fermi level (ef) is located at the bottom of a valley and originate mainly from the 5d electrons of re. population analyses suggest that the chemical bonding in re3n and re2n has predominantly covalent character with mixed covalent and ionic characteristics. the dielectric function, reflectivity, absorption coefficient, refractive index, electron energy-loss function and optical conductivity are presented in an energy range for discussing the optical properties of re3n and re2n. basic mechanical properties, such as elastic constants cij, bulk modulus b and shear modulus g are calculated. The young’s modulus e, poisson's ratio ν and bh/gh are also predicted. results conclude that the hexagonal phase re3n and re2n are mechanical stable and behaves in a ductile manner. polycrystalline elastic anisotropy is also derived from polycrystalline bulk modulus b and shear modulus g.

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

MRS Advances ◽  
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.

First-principles studies of pure and fluorine substituted alanines

2016 ◽  
Vol 30 (14) ◽  
pp. 1650079 ◽  
Author(s):  
Sardar Ahmad ◽  
Hamide Vaizie ◽  
H. A. Rahnamaye Aliabad ◽  
Rashid Ahmad ◽  
Imad Khan ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Structural Parameters ◽  
Wide Band ◽  
Electromagnetic Spectrum ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Direct Band ◽  
Indirect Band Gap

This paper communicates the structural, electronic and optical properties of L-alanine, monofluoro and difluoro substituted alanines using density functional calculations. These compounds exist in orthorhombic crystal structure and the calculated structural parameters such as lattice constants, bond angles and bond lengths are in agreement with the experimental results. L-alanine is an indirect band gap insulator, while its fluorine substituted compounds (monofluoroalanine and difluoroalanine) are direct band gap insulators. The substitution causes reduction in the band gap and hence these optically tailored direct wide band gap materials have enhanced optical properties in the ultraviolet (UV) region of electromagnetic spectrum. Therefore, optical properties like dielectric function, refractive index, reflectivity and energy loss function are also investigated. These compounds have almost isotropic nature in the lower frequency range while at higher energies, they have a significant anisotropic nature.

scholarly journals Physical Properties of XN (X = B, Al, Ga, In) in the Pm−3n phase: First-Principles Calculations

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1280 ◽  
Author(s):  
Qidong Zhang ◽  
Yucong Zou ◽  
Qingyang Fan ◽  
Yintang Yang
Keyword(s):  
Shear Modulus ◽  
Poisson’S Ratio ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Poisson's Ratio ◽  
First Principles Calculations ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Debye Temperatures ◽  
Direct Band

Three direct semiconductor materials and one indirect semiconductor material, Pm−3n XN (X = B, Al, Ga, In), are investigated in our work, employing density functional theory (DFT), where the structural properties, stability, elastic properties, elastic anisotropy properties and electronic properties are included. The shear modulus G and bulk modulus B of Pm−3n BN are 290 GPa and 244 GPa, respectively, which are slightly less than the values of B and G for c-BN and Pnma BN, while they are larger than those of C64 in the I41/amd phase. The shear modulus of Pm−3n BN is the greatest, and the shear modulus of C64 in the I41/amd phase is the smallest. The Debye temperatures of BN, AlN, GaN and InN are 1571, 793, 515 and 242 K, respectively, using the elastic modulus formula. AlN has the largest anisotropy in the Young’s modulus, shear modulus, and Poisson‘s ratio; BN has the smallest elastic anisotropy in G; and InN has the smallest elastic anisotropy in the Poisson’s ratio. Pm−3n BN, AlN, GaN and InN have the smallest elastic anisotropy along the (111) direction, and the elastic anisotropy of the E in the (100) (010) (001) planes and in the (011) (101) (110) planes is the same. The shear modulus and Poisson’s ratio of BN, AlN, GaN and InN in the Pm−3n phase in the (001), (010), (100), (111), (101), (110), and (011) planes are the same. In addition, AlN, GaN and InN all have direct band-gaps and can be used as a semiconductor within the HSE06 hybrid functional.

STUDY OF THE ELECTRONIC PROPERTIES OF CrO2 USING DENSITY FUNCTIONAL THEORY

2010 ◽  
Vol 24 (20) ◽  
pp. 2187-2193 ◽  
Author(s):  
M. P. GHIMIRE ◽  
SANDEEP ◽  
R. K. THAPA
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Wide Band ◽  
Local Spin Density Approximation ◽  
Wide Band Gap ◽  
Metallic Behavior ◽  
Functional Theory ◽  
Rutile Structure ◽  
Half Metallic ◽  
Direct Band

CrO 2 has a wide band gap for "down" spins and the Fermi level lies in the middle of the band gap. Calculations based on the local-spin density approximation (LSDA) has been performed to investigate the electronic and physical properties of CrO 2 in the rutile structure (P42/mnm). We considered the semicore electrons as valence electrons and found that CrO 2 appears to be half-metallic with a direct band gap of 1.8 eV in spin-down and has metallic behavior in spin-up configurations.

scholarly journals Properties of Novel Non-Silicon Materials for Photovoltaic Applications: A First-Principle Insight

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2006 ◽  
Author(s):  
Murugesan Rasukkannu ◽  
Dhayalan Velauthapillai ◽  
Federico Bianchini ◽  
Ponniah Vajeeston
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Crystalline Silicon ◽  
Visible Region ◽  
Initial Population ◽  
First Principle ◽  
Direct Band Gap ◽  
Depth Analysis ◽  
Photovoltaic Applications ◽  
Direct Band

Due to the low absorption coefficients of crystalline silicon-based solar cells, researchers have focused on non-silicon semiconductors with direct band gaps for the development of novel photovoltaic devices. In this study, we use density functional theory to model the electronic structure of a large database of candidates to identify materials with ideal properties for photovoltaic applications. The first screening is operated at the GGA level to select only materials with a sufficiently small direct band gap. We extracted twenty-seven candidates from an initial population of thousands, exhibiting GGA band gap in the range 0.5–1 eV. More accurate calculations using a hybrid functional were performed on this subset. Based on this, we present a detailed first-principle investigation of the four optimal compounds, namely, TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO. The direct band gap of these materials is between 1.1 and 2.26 eV. In the visible region, the absorption peaks that appear in the optical spectra for these compounds indicate high absorption intensity. Furthermore, we have investigated the structural and mechanical stability of these compounds and calculated electron effective masses. Based on in-depth analysis, we have identified TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO as very promising candidates for photovoltaic applications.

scholarly journals First principles calculations on theoretical band gap improvement of IIIA-VA zinc-blende semiconductor InAs

2020 ◽  
Vol 31 (12) ◽  
pp. 2050178
Author(s):  
Waqas Mahmood ◽  
Arfan Bukhtiar ◽  
Muhammad Haroon ◽  
Bing Dong
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Local Density ◽  
Lattice Parameter ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Zinc Blende ◽  
Valence States ◽  
Direct Band ◽  
Experimental Findings

The structural, electronic, dielectric and vibrational properties of zinc-blende (ZB) InAs were studied within the framework of density functional theory (DFT) by employing local density approximation and norm-conserving pseudopotentials. The optimal lattice parameter, direct band gap, static dielectric constant, phonon frequencies and Born effective charges calculated by treating In-4d electrons as valence states are in satisfactory agreement with other reported theoretical and experimental findings. The calculated band gap is reasonably accurate and improved in comparison to other findings. This work will be useful for more computational studies related to semiconductor devices.

Electronic Properties of Calcium and Zirconium Co-Doped BaTiO3

2020 ◽  
Vol 1010 ◽  
pp. 308-313
Author(s):  
Akeem Adekunle Adewale ◽  
Abdullah Chik ◽  
Ruhiyuddin Mohd Zaki
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Of States ◽  
Energy Band ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Energy Band Gap ◽  
Wide Energy ◽  
Direct Band

Barium titanate (BaTiO3) is a perovskite based oxides with many potential application in electronic devices. From experimental report BaTiO3 has wide energy band gap of about 3.4 eV which by doped with Ca and Zr at A- and B- sites respectively can enhance their piezoelectric properties. Using first principles method within the density functional theory (DFT) as implement in Quantum Espresso (QE) with the plane wave pseudo potential function, the influence of the Ca and Zr doping in BaTiO3 are studied via electronic properties: band structure, total density of states (TDOS) and partial density of states (PDOS). The energy band gap calculated was underestimation which is similar to other DFT work. Two direct band gap where observed in Ba0.875Ca0.125Ti0.875Zr0.125O3 sample at Γ- Γ (2.31 eV) and X- X (2.35 eV) symmetry point.

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