Tl2Ba2Ca2Cu3O10的化学键性质和同质异能位移研究

Tl2Ba2Ca2Cu3O10 was reported to be a superconductor with a highest transition temperature of 125 K among the homologous series of Tl2Ba2Can-1CunO2n+4. The direct information on the Cu ion site at the atomic level is important for elucidating the superconductivity mechanism. The local bond properties of Tl2Ba2Ca2Cu3O10 were studied using the average band-gap model. The calculated results show that the covalency of Cu(1)-O bond is 0.561, and the average covalency of Cu(2)-O is 0.296. M(o)ssbauer isomer shifts of 57Fe in Tl2Ba2Ca2Cu3O10 were calculated using the chemical surrounding factor, defined by covalency and electronic polarizability. It is verified that for lower doping, Fe substitute the Cu at the Cu (1) site in forms of Fe3+ and Fe4+; for higher doping, Fe3+ and Fe4+ ion occupies Cu(1) and Cu(2) site respectively.The studies show that the determination of the correspondence between spectrum components and actual copper sites occupied by M(o)ssbauer nucleus was made easier with the aid of the calculation results of the chemical bond parameters.     

M，W型六角钡铁氧体化学键性质和穆斯堡尔谱位移研究

利用电介质的平均能带模型研究了M型、W型六角铁氧体的化学成键性质,计算了各晶位的共价性的穆斯堡尔同质异能位移,结果与实验值一致,确定了Fe^2+在W型铁氧体中所占晶位。     

高温超导体中Fe占位研究的一种半经验方法

利用一种半经验方法研究了高温超导体Y-124的化学键性质．阐明了Y-124的Mossbauer谱同质异能位移和化学键参数之间的关系．计算结果支持掺杂的铁元素是以Fe3 价态占据Y-124的平面正方形Cu(1)3 晶位的观点．表明从化学键的观点预测高温超导体性质的可能性．     

晶体化学键的介电理论及其应用

基于复杂晶体化学键的介电理论,提出了晶体的化学键参数、硬度、同质异能位移和非线性光学系数等物理量的计算方法。这些方法建立起了化学键与各宏观性质之间的定量关系,并适用于多种类型物质的计算。     

高温超导体（La1—xMx）2CuO4（M＝Ba，Sr）的化学键性质和Moessbauer谱研究

利用复杂晶体化学键电介质的平均能带模型研究了(La1—xMx)2CuO4(M＝Ba，Sr)的化学键特性，得到Cu—O键的平均共价性为0．3，La—O键的平均共价性为0．03。应用由共价性和极化率定义的化学环境因子计算了^57Fe在La2CuO4中的Moessbauer同质异能位移，确定了^57Fe在La2CuO中的价态和占位情况。     

六方硼碳氮化合物的溶剂热合成与表征

采用溶剂热合成方法,以无水乙腈、叠氮化钠和四氟硼酸钠为原料,以苯为溶剂,在温度为400℃条件下,成功合成出了硼碳氮(BCN)三元化合物.利用X射线粉末衍射(XRD)、Fourier变换红外光谱(FTIR)、透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线能谱(EDS)和电子能量损失谱(EELS)对合成产物进行了表征.XRD和SAED分析表明,合成产物为六方相,晶格常数为a=0.2678nm,c=0.6639nm;TEM结果表明,合成产物中存在纳米棒和四方柱状块体BCN;EELS和EDS分析表明,产物由B,C,N三种元素组成,化学式为B0.23C0.60N0.17;FTIR分析表明样品中存在C—N,B—C和B—N键,表明B,C,N三元素之间达到了原子级化合.     

Theoretical calculations of hardness and metallicity for multibond hexagonal 5d transition metal diborides with ReB_2 structure

The hardness, electronic, and elastic properties of 5d transition metal diborides with ReB_2 structure are studied theoretically by using the first principles calculations. The calculated results are in good agreement with the previous experimental and theoretical results. Empirical formulas for estimating the hardness and partial number of effective free electrons for each bond in multibond compounds with metallicity are presented. Based on the formulas, IrB_2 has the largest hardness of 21.8 GPa, followed by OsB_2(21.0 GPa) and ReB_2(19.7 GPa), indicating that they are good candidates as hard materials.     

高温超导体(La1-xMx)2CuO4(M=Ba，Sr)的化学键性质和M(o^)ssbauer谱研究

利用复杂晶体化学键电介质的平均能带模型研究了(La_(1-x)M_x)_2CuO_4(M=Ba,Sr)的化学键特性,得到Cu-O键的平均共价性为0.3,La-O键的平均共价性为0.03。应用由共价性和极化率定义的化学环境因子计算了~(57)Fe在La_2CuO_4中的Mossbauer同质异能位移,确定了~(57)Fe在La_2CuO_4中的价态和占位情况。     

InP纳米针和纳米管的合成及机制探讨

采用溶剂热法以金属In和白磷为原料合成出了InP纳米针;采用溶剂热法以金属In和红磷为原料,以十六烷基三甲基溴化铵(CTAB)为表面活性剂合成出了InP纳米管。然后,分别采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)等技术对InP纳米针和纳米管的形貌及晶体结构进行了表征。最后,探讨了InP纳米针和纳米管的形成机制,本工作将为InP半导体纳米材料在发光二极管、光纤通信等领域的应用提供一定帮助。