- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Semimetallicity and Negative Differential Resistance from Hybrid Halide Perovskite Nanowires
摘要： In the rapidly progressing field of organometal halide perovskites, the dimensional reduction can open up new opportunities for device applications. Herein, taking the recently synthesized trimethylsulfonium lead triiodide (CH3)3SPbI3 perovskite as a representative example, first-principles calculations are carried out and the nanostructuring and device application of halide perovskite nanowires are studied. It is found that the 1D (CH3)3SPbI3 structure is structurally stable, and the electronic structures of higher-dimensional forms are robustly determined at the 1D level. Remarkably, due to the face-sharing [PbI6] octahedral atomic structure, the organic ligand-removed 1D PbI3 frameworks are also found to be stable. Moreover, the PbI3 columns avoid the Peierls distortion and assume a semimetallic character, contradicting the conventional assumption of semiconducting metal-halogen inorganic frameworks. Adopting the bundled nanowire junctions consisting of (CH3)3SPbI3 channels with sub-5 nm dimensions sandwiched between PbI3 electrodes, high current densities and large room-temperature negative differential resistance (NDR) are finally obtained. It will be emphasized that the NDR originates from the combination of the near-Ohmic character of PbI3-(CH3)3SPbI3 contacts and a novel NDR mechanism that involves the quantum-mechanical hybridization between channel and electrode states. This work demonstrates the great potential of low-dimensional hybrid perovskites toward advanced electronic devices beyond actively pursued photonic applications.
关键词： semimetals,halide perovskite nanowires,first-principles calculations,negative differential resistance
更新于2025-09-23 15:22:29
-
Enhancement of monolayer SnSe light absorption by strain engineering: A DFT calculation
摘要： Strain effects on the electronic and optical properties of monolayer SnSe is studied by APW + lo method in DFT framework. The applied strains cause direct-indirect transition of SnSe band gap which is mainly constructed by s/p hybridization. The armchair εac and zigzag εzz reduce the unstrained band gap of 1.05 eV down to 0 eV at 12% compression, but at 12% tension, the band gap decreases to 0.726–0.804 eV. The band gap always increases under biaxial strain εb at at 12% compression to 12% tension. We observe an enhancement of real ε1(ω) and imaginary ε2(ω) parts of dielectric function by 14% ? 30% of magnitude, wider peak distribution to infrared and ultra-violet regions, and appearance of new peaks in the ε1(ω) and ε2(ω) spectrums. As a consequence, the light absorption α(ω) is significantly enhanced in the ultra-violet region and the absorption even starts at lower energy at infrared region.
关键词： Strain,Optical properties,Electronic band structure,First-principles,Monolayer SnSe
更新于2025-09-23 15:22:29
-
Elastic and optoelectronic properties of CaTa2O6 compounds: Cubic and orthorhombic phases
摘要： Using first principles density functional theory (DFT) simulations, the structural, electronic, optical and elastic properties of CaTa2O6 oxide for cubic and orthorhombic phases are studied by highly accurate (FP-LAPW) method within the GGA + U approximation. The calculated lattice parameters are consistent with available experimental data. The electronic band structure calculations have shown that the band gaps in CaTa2O6 are equal to 3.08 eV and 4.40 eV for the cubic and orthorhombic structures, respectively. For both the phases the main optical properties, e.g., absorption coefficient, dielectric constant, energy loss function, and reflectivity, refractive index, and extinction coefficient are calculated and discussed in detail in the spectral range 0-14 eV. Cubic and orthorhombic phases exhibit significantly different optical characteristics. The electronic bonding characters of CaTa2O6 with different symmetries are explored via charge density distribution mapping. Strong covalent bonding character dominates in both the phases of CaTa2O6. Elastic properties of CaTa2O6 for cubic and orthorhombic phases are also investigated. The stress strain method is used for the determination of elastic constants in both the phases. The bulk modulus, shear modulus, Young’s modulus, along with the important elastic anisotropy factors and Poisson’s ratio are studied in detail.
关键词： First principles density functional theory,GGA+U approximation,FP-LAPW method,Optical constants,Electronic band structure,electro technical materials
更新于2025-09-23 15:22:29
-
Infrared Spectroscopy on Electronic Structures of Platinum-group Metal Pernitrides MN2 (M = Ru, Rh, Ir, and Pt)
摘要： The electronic structures of platinum-group metal pernitrides MN2 (M = Ru, Rh, Ir, and Pt) were investigated via synchrotron radiation infrared spectroscopy and first-principles calculations. Measured reflectance spectra of marcasite-type RuN2 and RhN2 showed Drude-like responses, approaching 1 as the photon energy was decreased, whereas reflectance of arsenopyrite-type IrN2 and pyrite-type PtN2 became ~0.3 in the low photon energy region with a few features. These findings agreed well with the predictions of the metallic nature of marcasite-type RuN2 and RhN2 and the semiconducting properties of arsenopyrite-type IrN2 and pyrite-type PtN2, respectively. The measured reflectance spectra were also reasonably consistent with the calculated optical responses. The band gaps of IrN2 and PtN2 were estimated to be 0.8 and 2.1 eV, respectively, via first-principles calculation with a modified Becke–Johnson (MBJ) potential for the exchange potential.
关键词： first-principles calculation,platinum-group metal pernitride,infrared reflectance spectra,valence band electronic structure
更新于2025-09-23 15:22:29
-
The phase transition and optical properties of Cr2+-doped ZnSe under high pressure
摘要： The phase transition pressure, electronic structure, optical properties and stability for ZnSe and Cr2+:ZnSe with different doping concentrations were calculated by first-principles calculation based on density-functional theory. The phase transition pressure was calculated by enthalpy-pressure relation. The introduction of dopant (Cr2+) reduces the phase transition pressure, and the phase transition pressure decreases with the increase of doping concentration. The high pressure enhances the degeneracy of Cr-d orbitals. Under the high-pressure conditions, the absorption peak positions of Cr2+:ZnSe have obvious blue-shift. Meanwhile, the stability of structures for ZnSe and Cr2+:ZnSe were further confirmed by defect formation energy and elastic constants.
关键词： Phase transition pressure,Cr2+:ZnSe,First-principles calculation,Optical properties
更新于2025-09-23 15:22:29
-
Ab-initio study of electronic, optical, thermal, and transport properties of Cr <sub/>4</sub> AlB <sub/>6</sub>
摘要： Theoretical investigation of different physical parameters of Cr4AlB6 have been done within the framework of density functional theory. Cr4AlB6 is a no band gap material. Its Cr-3d states contributes the most at the Fermi level. Thermal properties are investigated using quasi-harmonic Debye model as implemented in Gibbs code for different values of pressure and temperature. Study of transport property suggests that its electrical conductivity increases nonlinearly with increase in temperature but the relative change in its value is very low whereas its thermal conductivity increases linearly with the increase in temperature and relative increase in thermal conductivity is very high. The behavior of Cr4AlB6 is anisotropic and property is ceramic. It has potential applications in making ceramic capacitors. Its reflectivity is high in low energy region. It suggests that material can be used as coating material for far-infrared radiation. Study of the transport property suggests that because of very high value of thermal conductivity, it can be used for heat sink applications.
关键词： optical properties,first principles,electronic properties,thermal properties,thermoelectric transport properties,structural properties
更新于2025-09-23 15:22:29
-
Electronic properties and optical behaviors of bulk and monolayer ZrS2: A theoretical investigation
摘要： In this paper, we study the di?erence in electronic and optical properties of bulk and monolayer zirconium sul?de by applying the APW + lo method in the framework of density functional theory. All calculation is performed at the energy level of visual light and higher ranging from 0 eV to 15 eV. Our results demonstrates that except for the underestimated band gap like other GGA calculation, the remain properties like dielectric function, the re?ectivity, absorption and loss energy are close to experiment. The valence band is constructed by mainly sulfur s/p-states and the lower portion of zirconium s/p/d-states. The conduction band is mostly donated by zirconium d-state. In contrast with bulk structure, the valence band maximum in monolayer has the triple peak at Γ point, making its monolayer be more sensitive to light absorption. The di-electric function has the highest peak at about 1.5–2.5 eV with remarkable anisotropy, beyond this level to the ultraviolet region the anisotropy decreases and almost disappears at energy larger than 10 eV. The absorption is at 106 x 10 cm4 for energy range 5–10 eV, while the re?ectivity is at its highest value of 30 %–50 % in the energy range from 0 to 8 eV. The energy loss of monolayer is higher than those of bulk. For optical and electronic properties, the monolayer show sharper peaks and their clear separation indicate the progressive application of monolayer zirconium sul?de.
关键词： Monolayer ZrS2,Strain,First-principles,Band structure,Optical properties
更新于2025-09-23 15:21:21
-
AIP Conference Proceedings [Author(s) DAE SOLID STATE PHYSICS SYMPOSIUM 2017 - Mumbai, India (26–30 December 2017)] - First principles calculations for interaction of tyrosine with (ZnO)3 cluster
摘要： First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.
关键词： (ZnO)3 cluster,Tyrosine,First Principles Calculations,Density Functional Theory,Gaussian basis set
更新于2025-09-23 15:21:21
-
A theoretical investigation of the glide dislocations in the sphalerite ZnS
摘要： The 90(cid:1) and 30(cid:1) partial glide dislocations in ZnS are investigated theoretically in the framework of the fully discrete Peierls model and first-principles calculation. It is found that there are four types of equilibrium cores for each kind of partial glide dislocation, which are named as the O-Zn-core, the B-Zn-core, the O-S-core, and the B-S-core, according to their geometrical feature and atomic ingredient at the core. For the 90(cid:1) partial dislocation, the O-Zn-core (double-period core) and the B-S-core (single-period core) are stable. The Peierls barrier heights of the O-Zn-core and the B-S-core are about 0:03 eV/? and 0:01 eV/?, respectively. For the 30(cid:1) partial dislocation, the O-Zn-core (double-period core) and the B-Zn-core (single-period core) are stable and their Peierls barrier heights are approximately the same as that of the O-Zn-core of the 90(cid:1) partial dislocation. The Peierls stress related to the barrier height is about 800 MPa for the 90(cid:1) partial dislocation with the B-S-core. The existence of unstable equilibrium cores enables us to introduce the concept of the partial kink. Based on the concept of the partial kink, a minimum energy path is proposed for the formation and migration of kinks. It is noticed that the step length in kink migration is doubled due to the core reconstruction.
关键词： glide dislocations,sphalerite ZnS,Peierls model,partial kink,first-principles calculation
更新于2025-09-23 15:21:21
-
Theory-Driven Heterojunction Photocatalyst Design with Continuously Adjustable Band Gap Materials
摘要： The utilization efficiency of hot carriers in photocatalyst is limited at present by their fast recombination. Heterojunction interface would reduce the recombination rate by effectively facilitating spatial separation of the hot electron and hole. Here, we establish a heterojunction photocatalyst design principle by using continuously adjustable band gap materials. This is demonstrated using first-principles calculations, and is subsequently validated by direct measurements of photocatalytic activity of ZnxCd1-xS-reduced graphene oxide (RGO) heterojunction as a proof-of-concept photocatalyst. Tuning the Zn/Cd ratio and/or the reduction degree of RGO can result into three types of heterojunction, and different conduction and valence band offsets by varying their band gap and positions of band edges. The modulation of efficient electron-hole separation at the interface is manifested by the consistency of calculated and experimental optical absorbance, and enhanced photocatalytical activity of ZnxCd1-xS-RGO heterojunction. This results can also rationalize the available experimental results of RGO-based composites. This design principle is broadly applicable to the development of other heterojunction materials ranging from photocatalysts and solar cells to functional electronic devices through interfacial band alignment engineering.
关键词： band gap,photocatalytic activity,RGO,heterojunction,ZnxCd1-xS,photocatalyst,first-principles calculations
更新于2025-09-23 15:21:21