二价过渡金属离子对类水滑石稳定性影响的理论研究

Theoretical Studies of Effect of Divalent Transition Metal Ions on the Stability of Layered Double Hydroxides

基于密度泛函理论(DFT),构建二元含铝水滑石[M3Al-LDHs-NO3(M=Fe,Co,Cu,Zn)]周期性计算模型,选取CASTEP程序模块对模型进行几何优化及性质分析,通过对各体系的晶胞参数、氢键、结合能、电子性质、态密度的分析,研究了不同二价过渡金属离子对类水滑石体系稳定性的影响。结果表明:对于M3Al-LDHs-NO3体系,随着M离子原子序数的增加,各体系结合能的绝对值逐渐降低,禁带宽度逐渐变窄,主客体间静电作用力逐渐减小,氢键强度逐渐减弱,静电作用力与氢键的协同作用导致各体系的稳定性逐渐下降;此外,对于用d区元素或ds区元素作为二价金属离子所构成的二元含铝水滑石体系,前者所合成的水滑石更稳定。

Based on the density functional theory(DFT), we proposed a periodic interaction model for layered double hydroxides M3Al-LDHs-NO3, where M represents the different divalent transition metal ions(M=Fe, Co, Cu, Zn). The CASTEP program was used to optimize the geometry and analyze the property of M3Al-LDHs-NO3. By analyzing the cell parameters, hydrogen-bonding, binding energies, electronic properties and density of states, the effects of divalent transition metal ions on the stability of layered double hydroxides were researched. The results show that the absolute value of the binding energy decreases, the value of the band gap decreases, the electrostatic interaction forces between the host layer and the guests decreases, and the strength of hydrogen-bonding energy weakens gradually, with the increasing of the atomic number of M ion. In addition, the electrostatic interaction and hydrogen-bonding play a coordinating role, decreasing the chemical stability of the system gradually with the increasing of the atomic number of M ion. Besides, the element in the d-block or ds-block was selected as the divalent metal ion, such as Fe, Co, Cu, Zn, then making up the Al-containing layered double hydroxides, but the former is more stable.