稀土氮化物ScN、YN微晶的制备与表征

利用直流电弧等离子体方法制备出稀土氮化物ScN、YN微晶,这是一种快速、低成本、高产量的新方法,可用来制备稀土金属氮化物。结构物性表征和能谱成分分析结果表明,所制备的ScN晶体为满足化学计量比的单晶,而YN晶体为非化学计量比的多晶,其中Y的含量高于N。综合XRD、EDS、HRTEM和PL结果分析表明,YN晶体主要由大量随机取向的单晶颗粒组成,单晶颗粒间分布着一些非晶的金属Y,光谱结果分析表明YN中存在大量的N空位。此外,对样品的微观结构形成机理进行了系统分析,由于Y族金属氮化物中有限组分较高的解离压力以及产物在生长过程中经历较高的淬火速率(103 K/s),导致YN解离而形成的Y金属团簇的无序排列,进而使其在冷却过程中形成了非晶结构。

Electronic structure of ScN and YN： density-functional theory LDA and GW approximation calculations

The desirable physical properties of hardness, high temperature stability, and conductivity make the early transition metal nitrides important materials for various technological applications. To learn more about the nature of these materials, the local-density approximation（LDA） and GW approximation i.e. combination of the Green function G and the screened Coulomb interaction W, have been performed. This paper investigates the bulk electronic and physical properties of early transition metal mononitridcs, ScN and YN in the rocksalt structure. In this paper, the semicore electrons are regarded as valance electrons. ScN appears to be a semimetal, and YN is semiconductor with band gap of 0.142 eV within the LDA, but are in fact semiconductors with indirect band gaps of 1.244 and 0.544 eV respectively, as revealed by calculations performed using GW approximation.

密度泛函理论研究Sc_n,Y_n和La_n(n=2—10)团簇的稳定性、电子性质和磁性

通过采用密度泛函理论对Sc2,Y2和La2基本性质的计算,选择在较优理论水平下系统地研究了Scn,Yn和Lan(n=2—10)团簇的几何结构、稳定性、电子性质和磁性及其随团簇尺寸的变化趋势.此同族三种团簇的稳定性由原子密堆集几何结构效应决定,幻数均表现出一致的结果.Lan团簇的能隙比Scn和Yn团簇的能隙大,计算获得了团簇的电离势和电子亲和势数据,Yn团簇的电离势与实验值相符,最小极化率规律可很好地表征团簇的稳定性.三种团簇均具有较大的磁矩,磁矩与团簇的自旋多重度、几何和电子结构密切相关,理论值与实验值符合较好,随着团簇尺寸的增加三种团簇的平均磁矩总体上都呈递减的趋势并有局部振荡的特征.