摘要
基于密度泛函理论,用CASTEP程序模块构建水滑石(CuxZn3-xAl-LDHs)周期性计算模型,进行模型的几何全优化,对各体系的结构参数、氢键、Mulliken电荷布居及结合能等进行分析,探讨体系中的Jahn-Teller效应和结构稳定性.计算结果表明,层板中Cu2+与Zn2+交错排列的构型比较稳定.随着层板上Cu2+取代Zn2+的量增多,晶胞对称性变差,但Cu2+的Jahn-Teller效应对中心Al3+的影响较小.CuxZn3-xAl-LDHs(x=0～3)体系中离子键逐渐变强,共价键逐渐变弱,体系整体上由共价型晶体向离子型晶体转变.体系中Jahn-Teller效应导致的畸变使主-客体作用力增强,其中静电作用力减弱,氢键强度变大,且氢键作用占优势.总体上,体系的结合能绝对值逐渐减小,稳定性降低,这对于合成含铜的LDHs材料具有理论指导意义.
We proposed a periodic interaction model for the layered double hydroxides,CuxZn3-xAl-LDHs.Based on density functional theory,the geometry of CuxZn3-xAl-LDHs was optimized with the CASTEP program.Jahn-Teller effect and the stability were investigated by analyzing the geometric parameters,hydrogen-bonding,charge populations,and binding energies.The results showed that the structure of staggered arrangement of Cu2＋ and Zn2＋ in the layer was relatively stable.As the amount of Cu2＋ substituted Zn2＋ in the layer increased,the symmetry of unit cell became weaker,and Jahn-Teller effect of the copper had little effect on the central Al3＋.The strength of electrovalent bond became stronger while the strength of covalent bond became weaker with the increase of Cu2＋ substituted Zn2＋ in the layer,so the covalent crystal of CuxZn3-xAl-LDHs transited to the ionic crystal gradually.The distortion caused by Jahn-Teller effect made an enhanced supermolecular interaction between the host layer and the guest,the strength of electrostatic interactions became weaker while the strength of hydrogen-bonding became stronger,and hydrogen-bonding was superior to the electrostatic interaction.In general,the absolute value of the binding energy decreased gradually with an increase in the number of Cu2＋,then the chemical stability of the system got worse,and it was significant for synthesis of Cu-LDHs.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第12期2438-2444,共7页
Chemical Journal of Chinese Universities
基金
浙江省自然科学基金(批准号:Y406069)资助
