A DFT study of pressure-induced phase transitions, structural and electronic properties of Cu2ZnSnS4

2016 ◽  
Vol 30 (16) ◽  
pp. 1650176 ◽  
Author(s):  
Yifen Zhao ◽  
Decong Li ◽  
Zuming Liu
Keyword(s):  
Phase Transitions ◽  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Theoretical Work ◽  
Functional Theory ◽  
Phase Transition Pressure ◽  
Structural And Electronic Properties ◽  
Direct Band

The structural properties, phase transitions, and electronic structures of Cu2ZnSnS4 (CZTS) in the three structures have been researched using the first-principles density functional theory (DFT). The results indicate that the energies of stannite (ST) and pre-mixed Cu–Au (PMCA) CZTS are higher than those of kesterite (KS) CZTS, indicating that the KS CZTS is more stable. We found the phase transition pressure between the KS and ST structures of CZTS is about 32 GPa. Moreover, for KS- and PMCA-CZTS, there exists in the mischcrystal phase between 52 GPa and 65 GPa. The band structures show that the KS- and ST-CZTS are direct band gap semiconductors. The band gaps of three-type CZTS increase with increasing pressure, and the maximum band gap of KS and ST structures for CZTS occurs at 50 GPa. However, PMCA CZTS possesses metal property. Furthermore, the PMCA CZTS translates from metal to the indirect semiconductor with increasing pressure. The results play an important role in future experimental and theoretical work for CZTS materials.

Indirect-Direct Band Gap Transition by Van Der Waals Interaction Engineering in MoS2/WS2 Bilayer Heterojunction

2014 ◽  
Vol 614 ◽  
pp. 70-74 ◽  
Author(s):  
Hai Ning Cao ◽  
Zhi Ya Zhang ◽  
Ming Su Si ◽  
Feng Zhang ◽  
Yu Hua Wang
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Direct Band Gap ◽  
The Density Functional Theory ◽  
Direct Band ◽  
Electric Filed

First principles calculations based on the density functional theory (DFT) are employed to estimate the electronic structures of bilayer heterostructure of MoS2/WS2. The dependences of the band structures on external electric field and interlayer separation are evaluated. The external electric filed induces a semiconductor-metal transition. At the same time, a larger interlayer separation, corresponding to a weaker interlayer interaction, makes an indirect-direct band gap transition happen for the heterojunction. Our results demonstrate that electronic structure tailoring of two-dimensional layered materials should include both spatial symmetry control and interlayer vdW interactions engineering.

scholarly journals First-principles Study of Electronic and Dielectric Properties of ZrO2 and HfO2

2002 ◽  
Vol 747 ◽  
Author(s):  
Xinyuan Zhao ◽  
David Vanderbilt
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Dielectric Response ◽  
Density Functional ◽  
Low Pressure ◽  
Dielectric Tensor ◽  
Phonon Modes ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Born Effective Charge

ABSTRACTUsing density-functional theory with ultrasoft pseudopotentials, we previously investigated the structural and electronic properties of the low-pressure (cubic, tetragonal, and monoclinic) phases of ZrO2 and HfO2, in order to elucidate phonon modes, Born effective charge tensors, and especially the lattice dielectric response in these phases. We now extend this previous work by carrying out similar calculations on the two high-pressure orthorhombic phases, and by providing density-of-states and band-gap information on all polymorphs. Our results show that the electronic structures and dielectric responses are strongly phase-dependent. In particular, the monoclinic phases of ZrO2 and HfO2 are found to have a strongly anisotropic dielectric tensor and a rather small orientational average () compared to the two other low-pressure phases. Our calculations show that is even smaller in the orthorhombic phases.

scholarly journals Stable GaSe-Like Phosphorus Carbide Monolayer with Tunable Electronic and Optical Properties from Ab Initio Calculations

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1937 ◽  
Author(s):  
Xiaolin Cai ◽  
Zhili Zhu ◽  
Weiyang Yu ◽  
Chunyao Niu ◽  
Jianjun Wang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Electronic Structures ◽  
Density Functional ◽  
Promising Candidate ◽  
Functional Theory ◽  
Electronic And Optical Properties ◽  
Direct Band Gap ◽  
Direct Band ◽  
Indirect Band Gap

On the basis of density functional theory (DFT) calculations, we propose a stable two-dimensional (2D) monolayer phosphorus carbide (PC) with a GaSe-like structure, which has intriguing electronic and optical properties. Our calculated results show that this 2D monolayer structure is more stable than the other allotropes predicted by Tománek et al. [Nano Lett., 2016, 16, 3247–3252]. More importantly, this structure exhibits superb optical absorption, which can be mainly attributed to its direct band gap of 2.65 eV. The band edge alignments indicate that the 2D PC monolayer structure can be a promising candidate for photocatalytic water splitting. Furthermore, we found that strain is an effective method used to tune the electronic structures varying from direct to indirect band-gap semiconductor or even to metal. In addition, the introduction of one carbon vacancy in such a 2D PC structure can induce a magnetic moment of 1.22 µB. Our findings add a new member to the 2D material family and provide a promising candidate for optoelectronic devices in the future.

Increased Malleability in Tetragonal Zrx Ti1−x O2 Ternary Alloys: First-Principles Approach

2017 ◽  
Vol 72 (6) ◽  
pp. 567-572
Author(s):  
F. Ayedun ◽  
P.O. Adebambo ◽  
B.I. Adetunji ◽  
V.C. Ozebo ◽  
J.A. Oguntuase ◽  
...  
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Ternary Alloys ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Direct Band ◽  
Indirect Band Gap ◽  
Projector Augmented Wave ◽  
Alloying Effects

AbstractTetragonal phase of ZrxTi1−xO2ternary alloys is studied using generalized gradient approximation (GGA) projector augmented wave-based density functional theory (DFT). The calculations are used to characterize alloying effects of Zr substituting Ti in tutile TiO2. Band gap calculations show a direct band gap atx=0, while at other concentrations, an indirect band gap is observed. Electronic structure analysis shows that Zr alloying is capable of lowering the band gap transition of ZrxTi1−xO2atx=1 by the presence of an impurity state of transition metal Zr 5S2on the upper edge of the valence band. The addition of Zr also results in the corresponding increment in lattice constant with the material becoming more ductile and malleable.

Direct band gap nature and optical response of BexMgyZn1−(x+y)Se

2016 ◽  
Vol 30 (03) ◽  
pp. 1650007
Author(s):  
Naeemullah ◽  
G. Murtaza ◽  
R. Khenata ◽  
S. Bin Omran
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Experimental Measurements ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Direct Band Gap ◽  
Direct Band ◽  
First Time ◽  
Ultraviolet Energy

For the first time, the electronic and optical properties of the quaternary Be[Formula: see text]Mg[Formula: see text]Zn[Formula: see text]Se alloy have been investigated using first-principles calculations within the framework of density functional theory (DFT). Variations in the direct band gap with the change in [Formula: see text] and [Formula: see text] compositions show agreement with the experimental measurements. Evaluation of the dielectric function and refractive index reveals the optical activity in the visible and ultraviolet energy regions.

scholarly journals First-principles Study of Electronic and Dielectric Properties of ZrO2 and HfO2

2002 ◽  
Vol 745 ◽  
Author(s):  
Xinyuan Zhao ◽  
David Vanderbilt
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Dielectric Response ◽  
Density Functional ◽  
Low Pressure ◽  
Dielectric Tensor ◽  
Phonon Modes ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Born Effective Charge

ABSTRACTUsing density-functional theory with ultrasoft pseudopotentials, we previously investigated the structural and electronic properties of the low-pressure (cubic, tetragonal, and monoclinic) phases of ZrO2 and HfO2, in order to elucidate phonon modes, Born effective charge tensors, and especially the lattice dielectric response in these phases. We now extend this previous work by carrying out similar calculations on the two high-pressure orthorhombic phases, and by providing density-of-states and band-gap information on all polymorphs. Our results show that the electronic structures and dielectric responses are strongly phase-dependent. In particular, the monoclinic phases of ZrO2 and HfO2 are found to have a strongly anisotropic dielectric tensor and a rather small orientational average () compared to the two other low-pressure phases. Our calculations show that is even smaller in the orthorhombic phases.

scholarly journals Band Structure of Sr Doped into Bulk Wurtzite ZnO: A DFT Study.

2021 ◽  
pp. 10-17
Author(s):  
Abdalla Abdelrahman Mohamed ◽  
Tasneem Babiker Abdalrahman
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Band Gap Energy ◽  
Unit Cell Parameters ◽  
Lattice Volume ◽  
Cell Parameters ◽  
Structural And Electronic Properties ◽  
Direct Band ◽  
Indirect Band Gap

This work investigates the structural and electronic properties of pure and Sr-doped ZnO using first principles density functional calculations (DFT). The calculations were carried out using GGA-BLYP functional. This functional underestimates the band gap value in semiconductors but does not affect the accuracy of the related properties of the crystals. The Sr-doping caused increase in lattice volume and slight distortions at the unit cell parameters in a wurtzite structure. The doping process presented increase in the band-gap energy Eg at low percentages 25%, 37.5% and 50% with indirect bang gap and direct band gap at high percentages 62.5%, 75%, 87.5% and 100%.which we can called it wide indirect band gap. These results can be use as a foundation for more in depth calculations which can be used on optical and Photo-catalytic applications.

First-Principles Investigations of Electronic, Dynamic and Thermodynamic Properties of α-MnO2

2014 ◽  
Vol 936 ◽  
pp. 591-595 ◽  
Author(s):  
Ai Min Hao ◽  
Na Qi Wang
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Dynamic Properties ◽  
Thermodynamic Quantities ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Direct Band Gap ◽  
Direct Band

We investigate the electronic, dynamic and thermodynamic properties of α-MnO2 using first-principles calculations based on density functional theory (DFT) with the GGA+U method. The results of electronic structures show that α-MnO2is a semiconductor with a direct band gap of 1.4 eV at Γ point. The results of dynamic properties indicate that the structure of α-MnO2 is dynamically unstable at ground-state. Several important thermodynamic quantities, such as entropy, enthalpy and Gibbs free energy, et al each as a function of temperature were presented.

scholarly journals First Principles Study of Electronic and Optical Properties of Pristine and X (Cu, Ag And Au) Doped BiOBr

2018 ◽  
Vol 22 (2) ◽  
pp. 63-69 ◽  
Author(s):  
Samir Paudel ◽  
Puspa Raj Adhikari ◽  
Om Prakash Upadhyay ◽  
Gopi Chandra Kaphle ◽  
Anurag Srivastava
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Ab Initio Approach ◽  
Indirect Band Gap ◽  
Standard Density

The electronic structures and optical properties of pristine BiOBr and Cu, Ag and Au doped BiOBr have been analyzed by using a standard density functional theory based ab-initio approach employing generalized gradient approximation through revised Perdew Burke Ernzerhoff type parameterization. The calculation shows that both the doped and pristine BiOBr have indirect band gap, the band gap of the pristine BiOBr found 2.22eV, whereas band gap significantly reduced after doping Cu, Ag and Au on BiOBr. The band gap of Cu, Ag and Au doped BiOBr are 1.2eV, 0.9eV and 1.76eV respectively. The optical properties have been studied through dielectric function, both pure and doped BiOBr shows anisotropic nature. Journal of Institute of Science and TechnologyVolume 22, Issue 2, January 2018, page: 63-69 

Difference in Electronic Structure between Diamond and Graphite

2012 ◽  
Vol 229-231 ◽  
pp. 74-77 ◽  
Author(s):  
Jian Hong Gong ◽  
Shu Xia Lin ◽  
Wang Li ◽  
Jun Gao
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Transition Energy ◽  
Wide Band ◽  
Direct Transition ◽  
Wide Band Gap ◽  
Covalent Bonds ◽  
Functional Theory ◽  
Structural And Electronic Properties

The structural and electronic properties of diamond and graphite were investigated by the first-principles total-energy pseudopotential method based on density functional theory. The band structure, DOS and PDOS were calculated. Results showed that diamond had a wide band gap, and its direct transition energy is 6.0 eV. But graphite’s band gap is about zero, meaning without transition energy. That explains the reasons of diamond acting as an insulator but graphite acting as a conductor. DOS and PDOS analysis results indicate both diamond and graphite are sp hybridization and p states contribute mostly to the bonding of crystal. While their covalent bonds style are different.

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