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1.
本文在独立电子近似的基础上,根据多重散射自洽场理论方法,计算了C2和C2+,C2-分子(离子)的电子结构,阐明了势形共振能量和上述分子(离子)电子数的关系,结果表明,随着电子数的减少,C原子2s-2p轨道杂化减弱,势形共振的能量将降低(如降低到阈值下,则势形共振消失)。
关键词: 相似文献
2.
基于密度泛函理论详细地研究了金属钛的小尺寸团簇的稳定结构及电子性质。具体采用的计算方法是B3LYP/CEP-121G。在这项工作中,我们发现计算的电子亲和势的值与实验值符合的很好,但与原先的理论研究有些不同。 相似文献
3.
在密度泛函理论的基础上,对Ga6N6团簇进行了第一性原理、全电子、从头计算,得到了10种可能的三维空间结构及其电子结构.其中最稳定结构的一对GaN原子的平均结合能为9.748 eV,因此是可能存在的.但与他人计算的Ga3N3和Ga5N5相比,Ga6N6团簇可能不属于"幻数"团簇.最稳定结构的Ga6N6团簇的费米面是部分占有的,能量为EF=-5.2972 eV,因此具有"金属性",但没有自旋磁矩.我们还计算了该结构的Ga6N6团簇的亲和势、电离能和电子跃迁能.这将有助于对GanNn团簇系列的结构和性质随n变化的研究. 相似文献
4.
采用基于密度泛函理论的第一性原理方法系统研究了Au与3d过渡元素构成的混合小团簇的结构、稳定性、电子结构及磁性,得到了Au与3d过渡元素构成的混合小团簇的稳定结构.计算结果表明,Au与3d元素可形成大量的低能异构体,特别是有些异构体在结构上极相近,这不同于共价或离子键类型的团簇.与纯过渡金属团簇类似,这类团簇也表现出复杂的磁性.过渡金属元素的磁矩相比体材料而言既有增强的、也有减弱的,与轨道的交换劈裂密切相关.对于基态构型,AuCr2,Au2Cr2关键词:
密度泛函理论
第一性原理方法
团簇
电子结构 相似文献
5.
6.
采用基于第一性原理的密度泛函理论平面波超软赝势法, 研究了Y掺杂SrTiO3体系的空间结构和电子结构性质, 得到了优化后体系的结构参数, 掺杂形成能, 能带结构和电子态密度. 对比掺杂浓度为0.125, 0.25, 0.33时,Sr1-xYxTiO3和SrTi1-xYxO3的掺杂形成能,发现Y替代Sr能形成更稳定的结构. 对Sr1-xYxTiO3(x=0, 0.125, 0.25, 0.33) 的结构进行了优化,结果表明Y替代Sr后, 随着掺杂浓度增大, 体系的晶格常数逐渐减小, 稳定性逐渐增强. 对不同掺杂浓度的Sr1-xYxTiO3能带结构的计算结果表明:纯净的SrTiO3是绝缘体, 价带顶在R点, 导带底在Γ点, 费米能级处于价带顶; 掺杂Y后, 费米能级进入到导带底中, 体系呈金属性;掺杂浓度越大,费米能级进入导带的位置越深,禁带宽度也近似变宽. 相似文献
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8.
用密度泛函方法研究了Inn(n=2-7)团簇的稳定结构和电子性质。结果表明:自旋多重度对结构的影响不大;对于基态结构,n≤5时为平面结构,n≥6时为立体结构,n=6为结构转变点;平均结合能曲线随团簇尺寸增大逐渐平缓;能隙、结合能的二阶差分和电离势随团簇尺寸的变化趋势完全一致,均反映出In4团簇的基态结构较为稳定,具有较强的非金属性。 相似文献
9.
用密度泛函方法研究了In_n(n=2~7)团簇的稳定结构和电子性质.结果表明:自旋多重度对结构的影响不大;对于基态结构,n≤5时为平面结构,n≥6时为立体结构,n=6为结构转变点;平均结合能曲线随团簇尺寸增大逐渐平缓;能隙、结合能的二阶差分和电离势随团簇尺寸的变化趋势完全一致,均反映出In_4团簇的基态结构较为稳定,具有较强的非金属性. 相似文献
10.
采用密度泛函理论(DFT)B3LYP方法在6-311+G(d,p)基组水平,对CaSi_n(n=1~10)的结构进行优化,得出各个尺寸下团簇处于最低能量的结构模型,并对其稳定性等物理化学性质进行理论研究,表明CaSi_2、CaSi_5和CaSi_9为幻数团簇. 相似文献
11.
Zheng Wen-Chen 《辐射效应与固体损伤》2013,168(3-4):323-328
Abstract The zero-field splitting D, the anisotropic g-factors g ∥, Δg(=g ∥ ? g ⊥) and the first excited state splitting Δ(2 E) for the trigonal Cr3+–VK center in KMgF3: Cr3+ crystals have been studied from Macfarlane's high-order perturbation formulas. From the studies, the local structure of the trigonal center is obtained. The local lattice distortions (i.e., the displacement directions of the ions in the center) are consistent with the expectation based on the electrostatic interaction. 相似文献
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13.
Nilesh J. Vasa Kouki Morishita Husayin Parhat Tatsuo Okada Mitsuo Maeda Osamu Uchino 《Optical Review》1997,4(1):A176-A179
Spectrally pure high-power tunable single-mode operation of a pulsed Ti3+:sapphire laser by a tunable injection-seeding is reported. The injection laser was a cw diode laser pumped, spectrally narrowed
tunable Cr3+:LiSrAlF6 (Cr3+:LiSAF) laser with a grating in the auxiliary cavity. Single-mode tunable operation of a pulsed Ti3+: sapphire ring oscillator was obtained at different wavelengths in the range between 818 nm and 848 nm with a typical linewidth
of 0.006 cm-1. To extend the applicability of this operation to a differential absorption lidar system, the single-mode Ti3+:sapphire oscillator output was amplified and a high energy output of 38 mJ was obtained with the same linewidth. 相似文献
14.
The impurity-induced charge density in jellium is calculated by solving the Schr?dinger equation self-consistently. The resulting
phase shifts have been used to estimate the value of residual resistivity for dilute Zr-H system, which comes out to be 0.50
μΘ cm/at.%. An alternative form of one-parameter-screened Coulomb potential, which is more suitable than the customary Thomas-Fermi
potential, is suggested. The calculated self-energy by using new potential is found close to its value obtained by Darbyet al. 相似文献
15.
The EPR parameters (g factors g i and hyperfine structure constants A i , where i=x, y, z) of Ti3+ ion at the tetrahedral Si4+ site of beryl crystals are calculated within the rhombic symmetry approximation from the high-order perturbation formulas based on the two-spin-orbit (SO)-parameter model. In these formulas both the contribution due to the SO coupling parameter of the central 3d1 ion and that of ligand ions are considered. From the calculations, the defect structure of the Ti3+ defect center in beryl crystal is estimated and the EPR parameters g x , g y , g z and A y are reasonably explained. The values of the parameters A x and A z (which were not reported) are suggested and remain to be checked by the further experimental studies. 相似文献
16.
Yang Jinlong Wang Kelin L. F. Donà dalle Rose F. Toigo 《Zeitschrift für Physik B Condensed Matter》1991,84(2):255-261
The electronic structure and spectrum of Cr3+ in LiCaAlF6 are investigated by using the discrete variatitional-local density functional (DV-LDF) method with embedded cluster model. The clusters (CrF6)3– withC
3,D
3d
andO
h
point group symmetries embedded in the crystal are treated. The one-electron energy levels, densities of states, orbital populations, spin polarization splittings and energies of some terms are calculated. The results show that the relaxation of F– ions around the Cr3+ impurity is inevitable, and that theD
3d
andO
h
(CrF6)3– clusters, with an extended bond-lengthR(Cr–F) chosen to be equal to 1.88 Å can represent this relaxation in a much better way. All the ligand-field transition energies, which are obtained from the transition-state energy and the Griffith parameters, as yielded by a restricted one-electron DV-LDF calculation, compare well with the experimental ones. 相似文献
17.
Ai-Jie Mao 《Molecular physics》2013,111(8):1033-1038
The local lattice structure and EPR, optical spectra for Cr3+ doped in RbCdF3 crystal have been studied by diagonalizing the complete energy matrices. The results show that the local structure of the Cr3+ ions in RbCdF3 exhibits a compressed distortion at the trigonal and tetragonal sites. The compressed distortion can be ascribed to the fact that the radius of Cr3+ ion is smaller than that of Cd2+ ion, and therefore Cr3+ ion will draw the fluorin ligands inwards. The variational ranges of the local structural parameters for Cr3+ doped in RbCdF3 crystal R =?1.9491 Å ~?1.9814 Å, θ?= 55.234° ~?55.286° at the trigonal site and R 1 =?1.8617 Å ~?1.8928 Å, R 2 =?1.9527 Å ~?1.9851 Å at tetragonal site are obtained respectively, and the EPR and optical spectra agree well with the experimental results. 相似文献
18.
Powder samples of hydrothermally grown Cr 3+ -doped Cs 2 NaGaF 6 crystals have been investigated with electron paramagnetic resonance spectroscopy at X - (9.5 v GHz) and Q -band (34 v GHz). Analysis of the spectra clearly demonstrates that there are two distinct Cr 3+ centres in the Cs 2 NaGaF 6 crystal, having nearly identical g factors, but differing largely from the viewpoint of their zero field splitting. By using the 53 Cr hyperfine spectra observed with electron nuclear double resonance spectroscopy, it is deduced that these centres have opposite signs for the zero field splitting. The spectroscopic properties of the Cr 3+ centres in the isostructural Cs 2 NaGaF 6 and Cs 2 NaAlF 6 crystals are compared and discussed. 相似文献
19.
H. Parhat N.J. Vasa M. Kidosaki T. Okada M. Maeda T. Mizunami O. Uchino 《Applied physics. B, Lasers and optics》2000,70(3):361-366
We describe a comparative study related to an influence of a feedback coupling on operating characteristics of a cw Cr3+:LiSrAlF6 (Cr3+:LiSAF) laser using an end-coupled fiber grating with different coupling configurations. To achieve a compact construction,
a direct butt-coupling of the fiber grating at the pump end of the Cr3+:LiSAF laser and pumping through the same fiber was considered. The feedback provided by the coupled fiber grating through
an end mirror was responsible for a spectrally narrowed output with a slope efficiency of 11%. However, the performance critically
depended on an amount of the feedback coupling. The feedback-coupling condition was improved considerably by using a lens-coupled
fiber grating at the pump end of the Cr3+:LiSAF crystal. A spectrally narrowed output of ≈0.15 cm-1 was obtained, and the output slope efficiency was measured as 27%. Theoretical modeling was also performed to understand
the effect of the feedback coupling and the results agreed well with the experimental observations.
Received: 23 April 1999 / Revised version: 3 August 1999 / Published online: 30 November 1999 相似文献
20.
Wei Ning 《Journal of magnetism and magnetic materials》2009,321(9):1159-1162
Electron spin resonance (ESR) study was carried out on La0.67Ca0.33Mn1−xFexO3 (x=0.0, 0.04) samples. The temperature dependence of the ESR spectra indicates the presence of phase separation above and below TC in x=0.0 and 0.04 sample, respectively. The increase of the g-value in the high-temperature region indicates the existence of local spin correlations even in the paramagnetic state. The activation energy obtained from both the temperature dependence of the ESR intensity and linewidth exhibits a smaller value in the Fe-doped sample. Our study suggests that the ferromagnetic spin correlations would be significantly weakened by a slight doping of Fe ions on Mn sites. 相似文献