Design of a Class of New sp2-sp3Carbons Constructed by Graphite and Diamond Building Blocks

The sp²–sp³-hybridized carbon allotropes with the advantage of two hybrid structures possess rich and fascinating electronic and mechanical properties and they have received long-standing attention.We design a class of versatile sp²–sp³carbons composed of graphite and diamond structural units with variable sizes.This class of sp²–sp³carbons is energetically more favorable than graphite under high pressure,and their mechanical and dynamical stabilities are further confirmed at ambient pressure.The calculations of band structure and mechanical properties indicate that this class of sp²–sp³carbons not only exhibits peculiar electronic characteristics adjusted from semiconducting to metallic nature but also presents excellent mechanical characteristics,such as superhigh hardness and high ductility.These sp²–sp³carbons have desirable properties across a broad range of potential applications.     

Novel Boron Nitride Polymorphs with Graphite-Diamond Hybrid Structure

Both boron nitride（BN） and carbon（C） have sp, s^p2 and sp³ hybridization modes, thus resulting in a variety of BN and C polymorphs with similar structures, such as hexagonal BN（h BN） and graphite, cubic BN（c BN）and diamond. Here, five types of BN polymorph structures are proposed theoretically, inspired by the graphitediamond hybrid structures discovered in a recent experiment. These BN polymorphs with graphite-diamond hybrid structures possess excellent mechanical propertie...     

Bonding and Mssbauer Isomer Shifts in (Hg, Pb)-1223 Cuprate

IntroductionThethirdmemberofthehomologousseriesofHg Ba2 Can - 1CunO2n + 2 (Hg 12 2 3)wasreportedtobeasuper conductoratthehighesttransitiontemperatureof 133K ,1whichmakesitthemostattractive.ThedirectinformationontheCuionsiteattheatomiclevelisimportantforelucidatingthesuperconductivitymechanism .Sotheneedforamicro scopicprobesuchasM ssbauerspectroscopyisself evident.AnumberofpapersonM ssbauerspectroscopyhavebeenre ported .2 Nevertheless ,therearestillcontroversiesconcerningthespectrumfitsan…     

Ab Initio Study of Structural and Electronic Properties of Hexagonal BC2N

We investigate hexagonal BC2N in graphite unit cells using the first-principles method and calculate the total energies, lattice parameters, and electronic band structures after full relaxation. It is shown that stable hexagonal BC2N should be stacked sequentially with one graphite layer and one h-BN layer. The density of states indicates that this structure should have metallicity.     

方钴矿化合物FexCo4-xSb12的高温高压合成及其电输运特性研究

采用高压合成技术,在1.5 GPa,900 K的合成压力和温度条件下成功合成出了系列Fe置换掺杂型方钴矿化合物FexCo4-xSb12 ,其中x＝ 0,0.2,0.6,0.8. 详细研究了FexCo4-xSb12 样品在300 K ~ 700 K温度范围内的电阻率、Seebeck系数和功率因子（S2σ）随温度和Fe掺杂量的变化关系. 研究结果表明：在测试温度范围内,随着温度的升高,样品的电阻率和Seebeck系数逐渐增大. 随着Fe含量的增加,样品的电阻率和Seebeck系数先增加后减小. 与常压下相同样品比较,高压合成方法制备的样品的电学输运特性有了明显的提高. 上述研究结果表明,高压合成技术在制备热电材料方面能够有效地提高样品的电输运特性.     

“非晶”晶体:短程原子结构无序的晶体

大约十年前,人类在高压原位研究中首次发现了一种由无序原子团簇按周期性排列而形成的特殊晶体,被称为“非晶”晶体。该发现改写了人类对晶体中要求原子结构长程和短程皆有序的定义,引起了科学家们的研究兴趣,科研人员对比开展了大量研究。本文对过去十年里在“非晶”晶体材料研究中的进展进行小结和展望,希望能够吸引更多研究者对此类材料进行深入的探索和研究,并推动此研究领域不断向前发展。     

EFFECTS OF THE QUALITY OF SUBSTRATE ON THE STRUCTURE AND SUPERCONDUCTING PROPERTIES OF Yba2Cu3O7-x THIN FILM

We have systematically investigated the structures, morphologies, microwave surface resistance, DC performances and the substrate qualities of three YBa₂Cu₃O_7-x(YBCO) thin films 30mm in diameter. The three samples deposited by the same process have been proved of different properties. It has been shown that the structure and superconducting properties of the thin film depend strongly on the quality of substrate.     

用于无屏蔽环境生物磁测量的倒装片式高温超导梯度计 *

采用φ50.8m (即2 in)YBCO*/YBCO/CeO₂ /YSZ/Si多层膜制成的磁通变换器与SrTiO₃ 双晶上制备的尺寸为10mm×5mm平面式DC-SQUID梯度计构成一个倒装片梯度计 .磁通变换器与平面梯度计之间的耦合系数为0.18.磁通变换器有效地提高了梯度计的磁场梯度分辨率.倒装片式梯度计在白噪声区的磁场梯度分辨率为73fT·cm^-1·Hz^{-1/ 2} ,在1Hz下 ,磁场梯度分辨率为596fT·cm^-1·Hz^{-1/ 2} .在无屏蔽条件下 ,采用该梯度计成功地测得了高质量心磁图 .     

EFFECTS OF THE QUALITY OF SUBSTRATE ON THE STRUCTURE AND SUPERCONDUCTING PROPERTIES OF Yba2Cu3O7-x THIN FILM

We have systematically investigated the structures, morphologies, microwave surface resistance, DC performances and the substrate qualities of three YBa₂Cu₃O_7-x(YBCO) thin films 30mm in diameter. The three samples deposited by the same process have been proved of different properties. It has been shown that the structure and superconducting properties of the thin film depend strongly on the quality of substrate.     

稀土夹杂物对Fe-C合金中初生奥氏体非均质形核的影响

本文采用二维点阵错配度的计算方法,详细计算了三种常见的稀土夹杂物作为Fe-C系合金中初生奥氏体非均质成核基底的有效性。认为稀土氧化物可以成为初生奥氏体的有效核心,而稀土硫化物则不能成为有效核心,这与初生δ相的结果恰好相反。