Structure and Dynamics on Metal-Nonmetal transition in Ionic Liquids

测量了熔融的铜(Cl1-x&Gt；1-x&Gt；Brx)混合物的声速、声衰减和密度，以研究其热力学和动力学性质。根据测量的超声速度和密度，得到了该系统的绝热可压缩性。观测到的压缩系数在Cu(Cl_&lt；0.2&gt；Brt_&lt；0.8&gt；)附近有最大值，这表明熔盐混合物中有很大的波动。对CuX(X=Cl，Br)和AgX(X=Cl，I)熔体在熔点附近进行EXAFS测量，研究了CuX(X=Cl，I)的局部结构。测得的铜-卤素和银-卤素的距离比用同位素替代法测得的距离短0.1a-0.2a。结果表明，在液态下形成了CuX(X=Cl，Br)和AgX(X=Cl，I)等团簇。中子衍射、声速和DEN…对液态铋镓合金进行了更多的密度测量，测量的温度高于相容间隙闭合的临界点。在临界浓度下，结构因子发生了显著的变化，绝热压缩系数的温度系数在混相间隙区域以上显示出较小的值。这表明，热搅动引起的空间涨落并不影响混相带隙区域的可压缩性，原子很容易重新排列成具有较小空间涨落的较好结构。用X射线和中子衍射法测量了液体Te在470℃和570℃的结构因子。根据这一差异计算了两种温度下的离子-电子关联函数和价电子分布。得到的电荷分布函数在熔化温度以上0.8A和1.7A附近有两个峰。它们分别对应于中心碲离子周围的孤对电子和共价键电子的分布。在570℃时，电子电荷分布在1.1a附近观察到单峰。这与液体Te中的局域电荷密度分布由非金属态向金属态转变相对应。较少

The ultrasonic velocity, sound attenuation and density measurements have been carried out for molten Cu(Cl_<1-x>Br_x) mixtures to investigate the thermodynamic and dynamical properties. The adiabatic compressibility of this system was obtained from the observed ultrasonic velocity and density. The observed compressibility has the maximum value around Cu(Cl_<0.2>Br_<0.8>), which suggests large fluctuaion in the molten salt mixtures. The sound attenuation shows large temperature dependence around the same composition.EXAFS measurement for molten CuX(X=Cl, Br) and agX(X=Cl, I) has been carried out near the melting temperature to study the partial structure. The obtained Cu-halogen and Ag-halogen distances are about 0.1A-0.2A shorter than the distances obtained from neutron deffraction measurement by isotopic substitution method and the results suggest the cluster formation such as a CuX(X=Cl, Br) and AgX(X=Cl, I) trimmer in the liquid state.Neutron diffraction, ultrasonic velocity and den … More sity measurements have been carried out for liquid Bi-Ga alloys along the liquidus curve and at temperatures above the critical point where the miscibility gap closes. A remarkable change in the structure factor has been observed at the critical concentration, and the temperature coefficient of the adiabatic compressibility shows rather small value above the miscibility gap region. This suggests that the spatial fluctuation due to the thermal agitation does not affect the compressibility in the miscibility gap region, and the atoms can easily be rearranged to have the preferable structure with smaller spatial fluctuations.The structure factors of liquid Te at 470C and 570C have been measured by X-ray and neutron diffraction. The ion-electron correlation function and valence electron distribution were evaluated from this difference at the two temperatures. The obtained charge distribution function shows two peaks at the distance around 0.8A and 1.7A just above the melting temperature. Those correspond to the distribution of the lone pair electrons and the covalent bonded electrons around a central tellurium ion, respectively. At 570C, single peak is observed at the distance around 1.1A in the electron charge distribution. This corresponds to the change of the local charge density distribution from non-metalllic state to metallic one in liquid Te. Less