首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 921 毫秒
1.
2.
3.
In this paper, the physical aspects of the cubic phase XCrO3 (X=Ca,Sr,Ba) perovskites are studied by employing full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. These compounds have been found stable in ferromagnetic (FM) phase since they possess lower energy in FM phase compared to non-FM phase and their stability is also confirmed by calculating the enthalpy of formation (ΔH). The electronic structures of these compounds are analyzed with Trans and Blaha modified Becke–Johnson potential (TB-mBJ) for both spin up and spin down channels, which indicate their half-metallic characters. Analysis of density of states (DOS) shows major contributions of O-2p states in the valence band and Cr 3d-state in conduction band. A comparative analysis of crystal field effect (ΔEcrystal) and the exchange energies (direct Δx(d) and indirect Δx(pd)) tells about the main part of electronic spin in ferromagnetic character. The calculated magnetic moments make these compounds favorable for spintronic applications. In the end, thermoelectric parameters are computed for 200 K–800 K temperature range to explore potential of these compounds for applications in renewable energy devices.  相似文献   

4.
5.
《Radiation measurements》2007,42(4-5):719-722
Luminescence and luminescence excitation under VUV radiation of ABP2O7 (A=Na, K, Cs; B=Al, In) double phosphates are studied. Two emission bands peaking near 330 and 420 nm are common for investigated ABP2O7 crystals. The band structure and partial densities of electronic states of perfect KAlP2O7, LiInP2O7 and NaTiP2O7 crystals are calculated by the full-potential linear-augmented-plane-wave (FLAPW) method. It is found that the structures of the conduction bands of ABP2O7 crystals, which have different B cations, are appreciably different. Experimental results are compared with results of calculations of the electronic structure. Assumptions concerning the origin of luminescence in double phosphates are made.  相似文献   

6.
7.
8.
9.
Antiperovskite manganese nitrides Mn3(Cu0.6SixGe0.4?x)N (x=0.05, 0.1, 0.15) were prepared and their negative thermal expansion, magnetic and specific heat properties were investigated. A frozen state with a freezing temperature was found at ~207 K in Mn3(Cu0.6Si0.15Ge0.25)N. This indicates that Mn3(Cu0.6Si0.15Ge0.25)N exhibits a spin glass state at low temperatures. We discussed the cause of spin glass behavior and correlated this spin glass behavior with broadening of the negative thermal expansion operation-temperature window of the manganese nitrides Mn3(Cu0.6Si0.15Ge0.25)N.  相似文献   

10.
11.
An intermediate phase (labeled I phase) with dithering cycles between the L-mode and H-mode has been observed and experimentally characterized on Experimental Advanced Superconducting Tokamak (EAST). A typical characteristics of the I phase is that the Dα signal, edge density fluctuation level and edge radiation show several kHz periodical oscillation. The analysis shows that the dithering event is at least 2 cm inside the separatrix and extends into the scrape-off layer (SOL) region. It is found that this dithering occurs in plasma with double null (DN) or upper single null (USN) configuration and cannot be observed in plasma with lower single null (LSN) configuration where the ion B×?B drift direction is ‘unfavorable’, i.e. away from the X-point, in this device. The dithering cycle length (Δtdither) has no clear dependence on the heating power. Both stored energy and density increase during the dithering phase and the increasing rates decrease with Δtdither. The evolution of density profiles during the L–I–H transition is analyzed and presented.  相似文献   

12.
13.
14.
15.
16.
17.
18.
19.
We investigate the photoluminescence (PL) properties of silver/porous-silicon (Ag/PSi) nanocomposites prepared by metal-assisted etching in Ag2O/HF solution, on the basis of steady-state and time-resolved PL spectroscopy measurements. The PL intensity and peak position are strongly dependent on the Ag2O concentration. Time-resolved PL measurements reveal that the nonradiative rate decreases with an increase in the Ag2O concentration for the Ag/PSi nanocomposites. It is found from x-ray photoelectron spectroscopy measurements that the decrease in the nonradiative rate is caused by the formation of SiO2 layers on the PSi surfaces. Further, the number of light-emitting Si nanocrystals in the nanocomposites, which is estimated from the PL decay rate and PL intensity, increases with the Ag2O concentration. From the wavelength dependence of the PL decay rate, it is found that the nonradiative rate is considerably dispersive, i.e., the shorter the wavelength, the higher the nonradiative rate.  相似文献   

20.
Mixed traffic flux composed of crossing pedestrians and vehicles extensively exists in cities. To study the characteristics of the interference traffic flux, we develop a pedestrian-vehicle cellular automata model to present the interaction behaviors on a simple cross road. By realizing the fundamental parameters (i.e. injecting rates α1, α2, the extracting rate β and the pedestrian arrival rate αP), simulations are carried out. The vehicular traffic flux is calculated in terms of rates. The effect of the crosswalk can be regarded as a dynamic impurity. The system phase diagrams in the (α1,αP) plane are built. It is found that the phase diagrams consist essentially of four phases namely Free Flow, Congested, Maximal Current and Gridlock. The value of the Maximal current phase depends on the extracting rate β, while the Gridlock phase is achieved only when the pedestrians generating rate is higher than a critical value. Furthermore, the effect of vehicles changing lane (Pch1,Pch2) and the location of the crosswalk XP on the dynamic characteristics of vehicles flow are investigated. It is found that traffic situation in the system is slightly enhanced if the location of the crosswalks XP is far from the intersection. However, when Pch1, Pch2 increase, the traffic becomes congested and the Gridlock phase enlarges.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号