Effect of cation distribution on self-diffusion of molecular hydrogen in Na3Al3Si3O12 sodalite: a molecular dynamics study.
Effect of cation distribution on self-diffusion of molecular hydrogen in Na3Al3Si3O12 sodalite: a molecular dynamics study.
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阳离子分布对 Na3Al3Si3O12 方钠石中分子氢自扩散的影响：分子动力学研究。
DOI：
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发表时间：
2004
影响因子：
4.4
通讯作者：
J. Jansen
中科院分区：
文献类型：
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作者：
A. W. C. van den Berg;S. Bromley;E. Flikkema;J. Jansen
在800-1200 K的温度范围内，采用经典的分子动力学方法模拟了氢在钠铝硅方钠石（NaAlSi-SOD）中的扩散，考虑了主体骨架的完全柔性。从这些模拟中，自扩散系数被确定为温度的函数，并且在低平衡氢浓度下的氢吸收被估计为573 K。通过比较采用低能量完全有序的阳离子分布与使用较不有序的分布所获得的结果，在框架上的氢自扩散的阳离子分布的影响进行了研究。阳离子分布被发现有一个令人惊讶的大的影响扩散，这似乎是由于不同的阳离子分布，相关跳跃的情况下的有序分布的框架灵活性的差异，以及在两个系统中的扩散过程的不同性质。与我们以前报道的全硅方钠石（all-Si-SOD）的计算结果相比，钠铝方钠石的氢扩散系数在有序分布的情况下较高，在无序分布的情况下较低。在高温下（约1000 K），全硅超氧化物歧化酶和钠硅铝超氧化物歧化酶的吸氢速率相当，而在低温下（约400 K），全硅超氧化物歧化酶的吸氢速率较低。
The diffusion of hydrogen in sodium aluminum sodalite (NaAlSi-SOD) is modeled using classical molecular dynamics, allowing for full flexibility of the host framework, in the temperature range 800-1200 K. From these simulations, the self-diffusion coefficient is determined as a function of temperature and the hydrogen uptake at low equilibrium hydrogen concentration is estimated at 573 K. The influence of the cation distribution over the framework on the hydrogen self-diffusion is investigated by comparing results employing a low energy fully ordered cation distribution with those obtained using a less ordered distribution. The cation distribution is found to have a surprisingly large influence on the diffusion, which appears to be due to the difference in framework flexibility for different cation distributions, the occurrence of correlated hopping in case of the ordered distribution, and the different nature of the diffusion processes in both systems. Compared to our previously reported calculations on all silica sodalite (all-Si-SOD), the hydrogen diffusion coefficient of sodium aluminum sodalite is higher in the case of the ordered distribution and lower in case of the disordered distribution. The hydrogen uptake rates of all-Si-SOD and NaSiAl-SOD are comparable at high temperatures (approximately 1000 K) and lower for all-Si-SOD at lower temperatures (approximately 400 K).