Effects of pressure on structural,electronic, and mechanical properties of α,β,and γ uranium

The first-principles methods have been employed to calculate the structural, electronic, and mechanical properties of the α, β, and γ phases of uranium under pressure up to 100 GPa. The electronic structure has been viewed in forms of density of states and band structure. The mechanical stability of metal U in the α, β, and γ phases have been examined.The independent elastic constants, polycrystalline elastic moduli, as well as Poisson's ratio have been obtained. Upon compression, the elastic constants, elastic moduli, elastic wave velocities, and Debye temperature of α phase are enhanced pronouncedly. The value of B/G illustrates that α and γ phases are brittle in ground state.     

Features of Calculation of the Equation of State,Composition, and Conductivity for a Plasma of Dense,Supercritical Metal Vapors—a Plasma Fluid

Journal of Experimental and Theoretical Physics - The caloric and thermal equations of state, composition, and conductivity have been calculated for a supercritical aluminum plasma fluid. A...     

Nanoscale Physics ＆ Devices Laboratory,Institute of Physics,Chinese Academy of Sciences

Brief History Formerly known as Beijing Vacuum Physics Laboratory of Chinese Academy of Sciences since 1985, Nanoscale Physics ＆ Devices Laboratory （NPDL） was established in 2001. The mission of NPDL is to construct and study nanomaterials that address the challenges presented bythe national research strategy. For more than 20 years, NPDL has been dedicated to the study of fundamental physics related to nanomaterials and their applications in information and energy devices.     

Nanoscale PhysiCs ＆ Devlces Laboratory , nstitute of Physics, Chinese Academy of Sciences

概况 中国科学院物理研究所纳米物理与器件实验室的前身是中国科学院北京真空物理开放实验室,成立于1985年。二十多年来,实验室在科研工作中取得了一系列具有国际先进水平和国际领先水平的成果。目前实验室有四个研究组构成,实验室的运作特色是加强各研究组之间的交叉合作,发挥集体智慧,     

Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong

在近代量子力学的图像中，环绕着原子与分子的电子云具有各种不同的形态结构，一般在某一测定时间内，其形状为球状或哑铃状．这类形状通常称为电子轨道，它们可在飞秒量级的时间内明显地观测到．这些电子轨道也可在简并态(具有相同能量的量子态)间相互跃迁；如在相同轴上由垂直哑铃转变为水平哑铃等．     

First-principles calculation of the structural,electronic, elastic,and optical properties of sulfur-doping ε-GaSe crystal

The structural,electronic,mechanical properties,and frequency-dependent refractive indexes of GaSe_(1-x)S_x(x=0,0.25,and 1) are studied by using the first-principles pseudopotential method within density functional theory.The calculated results demonstrate the relationships between intralayer structure and elastic modulus in GaSe_(1-x)S_x(x=0,0.25,and 1).Doping of ε-GaSe with S strengthens the Ga-X bonds and increases its elastic moduli of C_(11) and C_(66).Born effective charge analysis provides an explanation for the modification of cleavage properties about the doping of e-GaSe with S.The calculated results of band gaps suggest that the distance between intralayer atom and substitution of S_(Se),rather than interlayer force,is a key factor influencing the electronic exciton energy of the layer semiconductor.The calculated refractive indexes indicate that the doping of ε-GaSe with S reduces its refractive index and increases its birefringence.     

Assignment of Photoelectron Spectra of MC2 （M= V, Cr, Fe, and Co）

Hybrid density functional theory （DFT） calculations are performed to study MC2 （M= V, Cr, Fe and Co） clusters in the neutral and anionic charge states. We find that the equilibrium geometries of MC2 and their anions are all cyclic structures with C2v symmetry, which agrees well with the previous theoretical studies. The Mulliken charge and spin populations of MC2 clusters and their anions are also calculated, and it is found that the electron charge transformations from anions to neutral molecules mainly take place on the M atoms. Time-dependent DFT is used to calculate the excited states, and a theoretical assignment for the features in the experimental photoelectron spectrum is given, which are in good agreement with the available experimental data.     

Synthesis,Characterization of 9, 9＇-Bianthracene and Fabrication of 9, 9＇-Bianthracene Field-Effect Transistors

We synthesize and purify 9, 9＇-bianthracene with the purity up to 96.4%. The electronic and crystallographic structures of 9, 9＇-bianthracene are studied. The results of a joint experimental investigation based on a combination of x-ray diffraction （XRD） spectra, hydrogen nuclear magnetic （HNMR） spectra, infrared absorption （FT-IR） spectra, and mass spectra （MS） of 9, 9＇-bianthracene are obtained. The uniform compact film is observed by an atomic-force microscope （AFM）. Organic field effect transistors （OFETs） with an active layer based on the synthesized 9, 9＇-bianthracene are fabricated for the first time. Its field-effect mobility is as large as 0.067 cm^2 /（V·s） and the on/off ratio is above 5 ×10^4. The result demonstrates that the oligomerization of a small semiconductor molecule is an effective method to develop high-mobility organic semiconductors.     

Quantitative estimates of the content of the metastable Si-XII,Si-III,and α-Si phases of silicon in the areas of indenter impressions

A quantitative estimate is presented of the specific and total volumes of the metastable Si-XII, Si-III, and α-Si phases of silicon in a locally strained (Berkovich pyramid) area. Calculations are performed using experimental data obtained via Raman spectroscopy and in situ registration of the Si-I → Si-II phase transitions of silicon under the indenter.     

Effect of purification,dehydration,and coagulation processes on the optical parameters of biological tissues

In this study,the effects of purification,dehydration,and coagulation processes on the absorption and reduced scattering coefficients of chicken liver tissues have been investigated by using a single integrating sphere system.The purification process performed on the tissue samples to remove blood residue has been found to cause a slight change in the optical parameters.Although the dehydration process brings about an increase in the absorption coefficient due to the water loss,no direct relationship has been observed between the reduced scattering coefficient and the dehydration level of the tissue.In addition,it has been observed that there was a relatively small increase in the absorption coefficient and a significant increase in the reduced scattering coefficient after the coagulation process.Therefore,it can be said that the optical penetration depth decreased significantly after dehydration and coagulation processes unlike blood purification.Moreover,fluence rate distributions inside the fresh,blood purified,dehydrated,and coagulated tissue models have been investigated by using the Monte Carlo modeling of photon transport in multilayered tissues simulation code.     

Study of Hard-sealed,Tunable,Photoelastic Birefringent Dual-frequency Lasers

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Application of the multireference equation of motion coupled cluster method,including spin–orbit coupling,to the atomic spectra of Cr,Mn, Fe and Co

The recently introduced multireference equation of motion (MR-EOM) approach is combined with a simple treatment of spin–orbit coupling, as implemented in the ORCA program. The resulting multireference equation of motion spin–orbit coupling (MR-EOM-SOC) approach is applied to the first-row transition metal atoms Cr, Mn, Fe and Co, for which experimental data are readily available. Using the MR-EOM-SOC approach, the splittings in each L-S multiplet can be accurately assessed (root mean square (RMS) errors of about 70 cm^?1). The RMS errors for J-specific excitation energies range from 414 to 783 cm^?1 and are comparable to previously reported J-averaged MR-EOM results using the ACESII program. The MR-EOM approach is highly efficient. A typical MR-EOM calculation of a full spin–orbit spectrum takes about 2 CPU hours on a single processor of a 12-core node, consisting of Intel XEON 2.93 GHz CPUs with 12.3 MB of shared cache memory.     

Reconstruction of all-electron orbitals from one-electron pseudowave functions and calculations of the intensities of Si X-ray emission spectra of Si, β-SiC,stishovite, and β-cristobalite crystals

The intensities of Si X-ray emission spectra of Si, β-SiC, stishovite, and β-cristobalite crystals are calculated. The wave functions of the initial and final states are obtained in the framework of the density-functional theory with the use of the norm-conserving and ultrasoft pseudopotentials. The all-electron crystal orbitals are reconstructed from the one-electron pseudowave functions. The probabilities of X-ray emission transitions are calculated by reconstructing the all-electron orbitals in two different gauges, namely, the length and velocity gauges. The calculated intensities are compared with the experimental spectra and the partial densities of states.     

Analysis of the common characteristics of the Hartmann,Ronchi, and Shack–Hartmann tests

An overview of the settings of the planes for the filters and observed patterns in the Hartmann and Ronchi tests is presented. Also a new set of filters for both test were developed. In a similar way, it is easy to extend this analysis to the Shack–Hartmann test, and to propose a new Null Shack–Hartmann filter.     

First-principles study of structural,electronic, and magnetic properties of Mn4XGe3 （X = Fe,Co,Ni）

In order to search for promising candidates for spintronic applications, this paper systematically studies three ternary compounds based on Mn5Ce3 by using a full-potential linearized augmented plane wave method within the density functional theory. Through structure optimization and electronic structure calculations, it finds that Mn4FeCe3 and MnaCoCe3 have much higher spin-polarization than original intermetallic compound Mn5Ce3, although the spin polarization of MnaNiCe3 is lower than that of Mn5Ce3. The calculated result is in agreement with experiment in the case of Mn4FeCe3. Both of them can be taken as promising candidates for spintronics applications because of their high spin-polarization and compatibility with semiconductors.     

First-principles study of Ar adsorptions on the （111） surfaces of Pd, Pt, Cu, and Rh

In the present paper we give a detailed report on the results of our first-principles investigations of Ar adsorptions at the four high symmetry sites on M （111） （M =Pd, Pt, Cu, and Rh） surfaces. Our studies indicate that the most stable adsorption sites of Ar on Pd （111） and Pt （111） surfaces are found to be the fcc-hollow sites. However, for Ar adsorptions on Cu （111） and Rh （111） surfaces, the most favorable site is the on-top site. The density of states （DOS） is analyzed for Ar adsorption on M （111） surfaces, and it is concluded that the adsorption behavior is dominated by the interaction between 3s, 3p orbits of Ar atoms and the d orbit of the base metal atoms.     

Role of compositional changes on thermal,magnetic,and mechanical properties of Fe-P-C-based amorphous alloys

This work aimed to tune the comprehensive properties of Fe-P-C-based amorphous system through investigating the role of microalloying process on the crystallization behavior,glass forming ability(GFA),soft magnetic features,and mechanical properties.Considering minor addition of elements into the system,it was found that the simultaneous microalloying of Ni and Co leads to the highest GFA,which was due to the optimization of compositional heterogeneity and creation of near-eutectic composition.Moreover,the FeCoNiCuPC amorphous alloy exhibited the best anelastic/viscoplastic behavior under the nanoindentation test,which was owing to the intensified structural fluctuations in the system.However,the improved plasticity by the extra Cu addition comes at the expense of magnetic properties,so that the saturation magnetization of this alloying system is significantly decreased compared to the FeCoPC amorphous alloy with the highest soft magnetic properties.In total,the results indicated that a combination of added elemental constitutes,i.e.,Fe69Co5Ni5Cu1P13C7 composition,provides an optimized state for the comprehensive properties in the alloying system.     

Effects of the 3d transition metal doping on the structural,electronic, and magnetic properties of BeO nanotubesEffects of the 3d transition metal doping on the structural,electronic, and magnetic properties of BeO nanotubesEffects of the 3d transition metal doping on the structural,electronic, and magnetic properties of BeO nanotubes

First-principles calculations have been performed on the structural, electronic, and magnetic properties of seven 3d transition-metal （TM） impurities （V, Cr, Mn, Fe, Co, Ni, and Cu） doped armchair （5,5） and zigzag （8,0） beryllium oxide nanotubes （BeONTs）. The results show that there exists a structural distortion around the 3d TM impurities with respect to the pristine BeONTs. The magnetic moment increases for V- and Cr-doped BeONTs and reaches a maximum for Mn-doped BeONT, and then decreases for Fe-, Co-, Ni-, and Cu-doped BeONTs successively, consistent with the predicted trend of Hund＇s rule to maximize the magnetic moments of the doped TM ions. However, the values of the magnetic moments are smaller than the predicted values of Hund＇s rule due to the strong hybridization between the 2p orbitals of the near O and Be ions of BeONTs and the 3d orbitals of the TM ions. Furthermore, the V-, Co-, and Ni-doped （5,5） and （8,0） BeONTs with half-metal ferromagnetism and thus 100% spin polarization character are good candidates for spintronic applications.