Correlation of Ionic Conductivity with Intersurface Phenomena in Superionic-Conductor-Superlattice

A computer simulation by a molecular dynamics method at constant volume has been performed to a model system which is composed of accumulating two different ionic conductors ：·沿c轴（z轴），AgI部分压缩，Ag_2S部分拉伸。Ag_2S部分中约3%的农药已转移到AgI部分。AgI-部分中AgI-部分的自扩散协同效应与单个AgI-系统中的40- 50%相比，而Ag_2S-部分中Agi的扩散协同效应与单个Ag_2S-系统中的30%相比。超晶格系统的离子行为比AgI系统或Ag_2S系统的任何物质都要大。计算建议提出了一种新材料的存在的可能性，其中一些材料具有较大的离子条件。在这种计算中，在一个固定的MD细胞的体积V中，粒子的运动的牛顿方程已被量化。总能量E已被控制，因此由模拟产生的推理是微型或（E，V，N）推理。然而，这些模拟的条件并不像那些通常在实验中显示的那样。通常的实验在恒定温度和恒定压力或（T，P，N）条件下进行。然后，我们现在正在对超晶格系统进行MD计算的恒定压力，同时还考虑到了电子的极化性。

A computer simulation by a molecular dynamics method at constant volume has been performed to a model system which is composed of accumulating two different ionic conductors :・・・AgI-Ag_2S-AgI-Ag_2S・・・. Along the c-axis (z-axis), AgI-parts are compressed and Ag_2S-parts are stretched. About 3% of Ag ions in Ag_2S-parts have been transfered to AgI-parts. The self-diffusion coefficient of Ag ions in AgI-parts decreases by 40-50 % compared with that in a single AgI-system, while the diffusion coefficient of Ag ions in Ag_2S-parts increases by 30 % compared with that in a single Ag_2S-system. The ionic conductivity of the superlattice-system is larger than that of either material of the AgI-system or Ag_2S-system. The calculation suggests the possibility of the existence of a new material which has a larger ionic conductivity.In this calculation, the newtonian equations of motion of the particles in a fixed MD cell of volume V have been solved numerically. The total energy E has been conserved, and thus the ensemble generated by the simulation is the microcanonical or (E,V,N) ensemble. But these conditions of simulation are not the same as those normally encountered in experiments. The usual experiments are performed under conditions of constant temperature and constant pressure or (T,P,N) conditions. Then we are now performing the MD calculation at constant pressure to the superionic superlattice-system, with also considering the electronic polarizability of anions.