A periodic interaction model was proposed for the copper-iron layered double hydroxides, CusFe-LDHs-yHzO (y=0-2). Based on density functional theory, the geometry of Cu3Fe-LDHs-yH2O was optimized using the CASTEP program. The distribution of NOi and H3O in the interlayer and the supermolecular interaction between host and guest was investigated by analyzing the geometric parameters, hydrogen-bonding, charge populations and stepwise hydration energy. Results indicated that when NO3 and H;O were inserted into the layers of the Cu3Fe-LDHs, there was a strong supramolecular interaction between the host layer and the guest, including hydrogen-bonding and electrostatic interaction. Hydrogen-bonding was superior to the electrostatic interaction in the hydration process. The strength of hydrogen bonding was ordered as Layer-Anion (L-A) > Anion-Water (A-W) > Layer-Water (L-W) > Water -Water (W-W). In Cu3Fe-LDHs-yH;O, the interlayer distance decreased slightly and then increased significantly with an increase in the number of interlayer water molecules. The Cu - O octahedral forms were stretched gradually because of the increased Jahn - Teller effect of Cu2'. The absolute value of the hydration energy decreased gradually with an increase in the number of water molecules. This suggested that the hydration of CujFe-LDHs reached a saturation state. The geometry of Cu3Fe-LDHs-1H2O is close to hexagonal where the metal distortion of the layer is weakest and the stability is strongest; the interlayer distance agrees the experimental value, therefore CujFe-LDHs-IH2O is a stable configuration.%构建铜铁水滑石[Cu3Fe-LDHs-yH2O(y=0-2)]周期性计算模型,采用密度泛函理论(DFT),选取CASTEP程序模块,对体系进行几何全优化.从结构参数、氢键、Mulliken电荷布居、逐级水合能等角度研究了层间NO3-和H2O的分布形态及其与水滑石(LDHs)层板的超分子作用,探究了水分子数目对体系姜-泰勒效应的影响.结果表明:Cu3Fe-LDHs-yH2O主客体间存在着较强的超分子作用力,主要包括氧键和静电作用,其中氢键作用在水合过程中起主导作用,氢键强度的顺序是层板-阴离子(L-A)型＞阴离子-水(A-W)型＞层板-水(L-W)型＞水-水(W-W)型;随着层间水分子数的增加,层间距先略微降低后显著升高,cu3Fe-LDHs体系的Cu-O八面体被逐渐拉长,层板Cu2+的姜-泰勒畸变程度逐渐增大,体系的逐级水合能绝对值逐渐降低,说明Cu3Fe-LDHs的水合程度不会无限增加,而是具有一个饱和值.Cu3Fe-LDHs-1H2O构型接近理想六方晶胞,层板金属畸变程度最小,稳定性最高,层间距与实验值较吻合,推测其为实验上合成的Cu3Fe-LDHs较稳定的构型.
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