Shen, PengZhou, DongLiu, ShuaiWang, Chao...
5页查看更多>>摘要：The dynamic process of individual magnetic moment is closely related to the formation or persistence of reverse nucleus in regions where there are usually low anisotropy and complicated stray fields. It is also associated with the propagation of reverse magnetic domain and therefore affects the coercivity of magnets. In this work, we studied the detailed rotation process of individual moment in changing magnetic field. The dependence of the direction of magnetic moment on the direction of anisotropy axis and magnetic field is interestingly complicated. With the angle between the anisotropy axis and magnetic field increasing for different value of the field, the direction of magnetic moment will show three different changing processes, that is, continuously increasing process, sine-like changing process and discontinuously changing process.
原文链接:
NSTL
Elsevier
Alam, MarwanWaheed, Hafiza SumairaUllah, HamidIqbal, M. Waqas...
7页查看更多>>摘要：Highly demanding efficiency, scaling and cost led the researchers to predict and synthesize two-dimensional transition metal dichalcogenides for advanced technology. Using the first-principles calculations, we study the optoelectronic properties, and device absorption efficiency of Janus SnSSe monolayer. The Janus SnSSe exist in two different phases, 1T and 2H structures. We find the 1T structure dynamically more stable than the 2H structure due lower energy and no-negative frequencies in the phonon spectra. The 1T SnSSe possess semiconducting nature with an indirect band-gap of 1.61 eV. The Janus SnSSe possesses a strong absorption having sharp absorption edges, showing the transition of electron to the conduction band from the valence band. We find that the Janus SnSSe strongly absorb light below 4.0 eV, which show its prominent applications for solar cell. A strong absorption from infra-red to the ultra-violet region of light spectrum make it promising in the optical devices. Furthermore, the wider band gap nature having strong device absorption-efficiency could make it suitable for the top cell in the tandem architecture.
原文链接:- NSTL
- Elsevier
Qin, XinzhanZhao, JianWei, RanCao, Yu...
9页查看更多>>摘要：Pyrophyllite [Al2Si4O10(OH)(2)] is mainly used in the field of refractories and super-hard materials due to its excellent thermal properties such as good heat resistance, stable chemical properties and crystal structure stability during heating. However, its thermodynamic properties have rarely been fully described at the atomic scale. In this study, the thermodynamic and thermoelastic properties of pyrophyllite are reported in detail, based on the first principles. Firstly, the relationship between the Helmholtz free energy and volume (E-V) under different temperatures was fitted using the quasi-harmonic approximation (QHA), which confirmed the thermal expansion effect of pyrophyllite at 0-900 K. Phonon dispersion curves at different temperatures showed that pyrophyllite maintained phase stability within a given temperature range (0-900 K). Furthermore, its elastic behaviors at 0, 300, 450, 600, 750, and 900 K are discussed. As the temperature increased from 0 K to 900 K, the elastic modulus of pyrophyllite decreased to varying degrees, which indicated that high temperature weakened its ability to resist external pressure. This elastic softening phenomenon was caused by the thermal expansion effect. The changes of Paugh's modulus ratio (G/B) clearly indicated that the ductility of pyrophyllite under high temperature (up to 900 K) was greater than that at 0 K. Overall, high temperature increases the volume of pyrophyllite and decreases its strength. Thus, when pyrophyllite is used in the field of refractories, the particle size and amount of pyrophyllite should be reasonably selected to achieve the balance between the volume stability and strength of the material. These findings enrich our theoretical knowledge of pyrophyllite behavior at high temperatures at the atomic scale, which is difficult to determine accurately using physical experiments.
原文链接:- NSTL
- Elsevier
Gong, LiYan, XinZhang, XiaLi, Yi...
9页查看更多>>摘要：Electronic structures and optical properties of S-passivated InAs nanowires are studied by first-principles. The computation is carried out on the InAs (110) surface, which has a low surface energy and is a common side facet of 111 -oriented zinc blende InAs nanowires. Through comparing different geometrical possibilities, it is found that S atoms prefer to insert the interchain bridge site, and occupy both the interchain bridge site and bridge site, for a non-diffused half-monolayer coverage and full non-diffused monolayer coverage, respectively. The electronic energy bands shift towards lower energy region and the band gap narrows after S adsorption. The density of states near Fermi level increases after S adsorption, indicating that S adsorption can enhance the conductivity and leads to a metallic-like nanowire surface. In addition, the adsorption of S significantly improves the absorption and optical conductivity of InAs nanowires in the low frequency range.
原文链接:- NSTL
- Elsevier
Al-Namshah, Khadijah S.Shkir, MohdIbrahim, Fatma A.Hamdy, Mohamed S....
10页查看更多>>摘要：In this report, pure ZnO and Co doped ZnO (1, 2.5, 5, 7.5 wt% of Co) nanoparticles were synthesized by using one-pot flash combustion synthesis technique. Structural, morphological, optical and photocatalytic properties of the prepared samples were analyzed by using different characterization techniques. The X-ray diffraction results shows the pure ZnO and Co:ZnO samples exhibits hexagonal wurtzite structure having preferential growth along the (101) plane without the presence of secondary phase impurities. The crystalline size of the 7.5% Co:ZnO sample was found to be higher with a value of 27.14 nm with low dislocation density and strain values of 1.36 x 10-3 and 4.38 x 10-3, respectively compared to the other prepared samples. The morphology of the prepared samples were obtained using FESEM analysis which revealed a non-uniform spherical shaped nanoparticles for pure ZnO and the morphology becomes uniform with the incorporation of the Co dopants. The e-mapping and the EDX results confirms the presence of Zn, O and Co elements. UV-Vis. absorption spectrum revealed that the inclusion of Co dopants in ZnO incorporation leads to higher absorption and decrease in band gap. The band gap values of ZnO are noticed to be reduced from 3.27 eV 2.81 eV with Co doping from 0 to 7.5 wt%. Photocatalytic performance of the prepared samples was evaluated in the decolourization reaction of methyl green aqueous solution under the illumination. The prepared Co doped ZnO samples exhibited several times higher photocatalytic activity than bare ZnO. The kinetic model was proposed and the rate constant for the decolourization reactions was calculated. The best performed sample was 5 wt% Co, in which the rate constant was 2.6 times higher than that of bare ZnO.
原文链接:- NSTL
- Elsevier
Mehboob, Muhammad YasirHussain, RiazAdnan, MuhammadIrshad, Zobia...
11页查看更多>>摘要：Non-fullerene acceptor (NFA) materials attracted a huge attention because of their tendency to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, we intended to demonstrate the efficient designing of a series of Rain-bow shaped materials (LB1 to LB5). These acceptor materials are designed by various end-capped modifications in a synthetically reported pi-linker CH1007 molecule (reference R). The photovoltaic, optoelectronic, structural-property relationship, and physiochemical properties are specifically realized by using density functional theory (DFT) and time-dependent (TD-DFT) at B3LYP/6-31G (d,p). Our designed materials (LB1 to LB5) significantly occupied a narrower energy bandgap (E-g) (E-g = 1.87-2.01 eV) in contrast to R and found highly red-shifted in absorption spectrum with lower excitation energies. The reorganization energy studies showed that the newly designed materials (LB1 to LB5) exhibited a better electronic mobility (lambda(h) = 0.0153 to 0.0190) as compared with R (lambda(h) = 0.0194). The higher open circuit voltage (V-oc), and lower binding energy (Eb) values suggested that these designed materials (LB1 to LB5) are best fitted to prepare highly efficient OSCs devices. To study the charge transfer behavior, a donor:acceptor (D:A) blend study has also been performed to estimate an efficient charge transport phenomenon at the D:A interface. The outcomes of all analysis suggested that this designed series (LB1 to LB5) could be effective for the future development of highly efficient OSCs devices.
原文链接:- NSTL
- Elsevier
Kaushik, VishakhaPathak, SachinSharma, H.Sachdev, S....
7页查看更多>>摘要：A theoretical approach using first-principle calculations of the density of states (DOS) of functionalized carbon nanotubes (CNTs) is carried out to understand their enhanced electron field emission (FE) properties. The theoretical functionalization of CNTs is perceived using hydrogenation (H/O-H) and oxidation methods. In order to investigate the enhancement in the FE properties of functionalized CNTs, both single-walled carbon nanotubes (SWCNT) and double-walled carbon nanotubes (DWCNT) are studied. The work function is observed to be more decreased in case of zigzag SWCNT (phi = 3.32 for oxygenated SWCNT) as compared to others SWCNT. The dependence of DOS on zigzag/armchair edge functionalization has also been investigated to reveal the impact of DOS on FE. The observed results indicate that edge functionalization of CNTs leads to significant changes in the band structure, DOS, and work functions. The shifting of DOS away from the Fermi level and decrease in work function is evidenced owing to the reduction in the curvature effect of CNT. Also, due to enhanced DOS near the Fermi level, making them a better proposition for FE applications. Our calculations provide an in-depth insight into the functionalization mechanism to understand the enhanced FE properties from them.
原文链接:- NSTL
- Elsevier
Shu, YaoXiong, YongnanLuo, XingZhang, Zhibo...
13页查看更多>>摘要：The first principles method was utilized to study the interfacial properties of the TiB2 reinforced copper matrix materials. The interfacial stabilities were studied initially via the works of adhesion and interfacial energies. According to the results, TT-OT (Ti-terminated TiB2/Cu "OT" stacking) and BT-HCP (B-terminated TiB2/Cu "HCP" stacking) were confirmed to be the most stable interfaces. The charge density distribution, charge density difference, electronic localization function and partial density of state were analyzed for TiB2/Cu interfaces. The results indicate that Ti-terminated TiB2(0001)/Cu(111) interfaces were more inclined to form the metallic bond, while the B-terminated TiB2(0001)/Cu(111) interfaces were likely to form the ionic bond. Moreover, the interfacial elastic energy, interfacial fracture toughness and ultimate tensile tress were carried out to make clear of fracture mechanism of the TiB2(0001)/Cu(111) interfaces. The TT-OT and BT-HCP were confirmed to be the two most stable interfaces due to their largest interfacial elastic energies. The computational ultimate tensile tress for Ti-terminated TiB2(0001)/Cu(111) and B-terminated TiB2(0001)/Cu(111) interfacial models were 23 GPa and 25 GPa, respectively.
原文链接:- NSTL
- Elsevier
Engelbrecht, J. A. A.Minnaar, E. G.van Dyk, E. E.Westraadt, J. E....
6页查看更多>>摘要：A formula for the calculation of the refractive index of AlXGa1-XN in the infrared region has previously been proposed. In this paper, the validity of the proposed model is assessed against the multi-oscillator model which simulates the infrared reflectance of AlXGa1-XN epilayers. Acceptable agreement was found between the two models for wavenumbers greater than 3500 cm(-1). Additional validation for the earlier proposed formula is obtained by the calculation of epilayer thicknesses of AlXGa1-XN samples in the infrared region.
原文链接:- NSTL
- Elsevier
Rathore, Mahendra SinghVinod, ArunAngalakurthi, RambabuPathak, A. P....
9页查看更多>>摘要：Role of oxygen pressure on the structural, optical and photoluminescence properties of GeO2 thin films grown by pulsed laser deposition has been investigated. X-ray diffraction reveals the hexagonal phase of GeO2 films. The lattice parameters of grown films are evaluated using Rietveld refinement. X-ray photoelectron spectroscopy results confirm the GeO2 formation. Rutherford backscattering spectrometry was used to determine the elemental composition and thickness of films. The optical transmittance of films increases from 85 to 93% and optical bandgap from 5.2 to 5.55eV with an increase in oxygen pressure from 100 to 200 mTorr. Strong PL emission around 396 nm is observed and the intensity of PL emission increases with increase in oxygen pressure from 100 to 300mTorr. Oxygen pressure of 200mTorr is found to be optimum for the growth of high-quality crystalline GeO2 thin films. The obtained PL results show the potential use of GeO2 thin films for optical applications.
原文链接:- NSTL
- Elsevier
