CAJ | 학술논문

通过构建镁锡水滑石(Mg_3Sn-LDHs-yH_2O)周期性计算模型,基于密度泛函理论,用CASTEP程序模块,进行模型的几何全优化.对各体系的结构参数、Mulliken电荷布居、态密度(DOS)、逐级水合能等进行分析,探究客体CO_3~(2-)和H_2O的分布形态及其与主体层板的超分子作用.结果表明,[Mg_Sn_2(0H)_(16)]~(4+)层间插入客体阴离子CO_3~(2-)和水分子后,主客体问存在着较强的超分子作用力,主要包括静电和氢键作用,且氢键作用在水合过程中起主导作用,总体上层板-水(L-W)型,层板-阴离子(L-A)型氢键强度要强于阴离子-水(A-w)型/水-水(W-W)型氢键.随着层间水分子的增多,层间距先增大后又稍降低.当y=0、1时,客体所在的平面与主体层板平行,且与两层板的距离基本相等;当y=2、3时,客体以偏向某一层板的形式存在.与层间H_2O相比,层问阴离子CO_3~(2-)对体系态密度的影响更显著,层板与CO_3~(2-)的总体作用力大于与H_2O的总体作用力.随着水分子数的增加,Mg_3Sn-LDHs-yH_2O体系的逐级水合能绝对值逐渐降低,说明Mg_3Sn-LDHs的水合程度不会无限增加,而是具有饱和量.
통과구건미석수활석(Mg_3Sn-LDHs-yH_2O)주기성계산모형,기우밀도범함이론,용CASTEP정서모괴,진행모형적궤하전우화.대각체계적결구삼수、Mulliken전하포거、태밀도(DOS)、축급수합능등진행분석,탐구객체CO_3~(2-)화H_2O적분포형태급기여주체층판적초분자작용.결과표명,[Mg_Sn_2(0H)_(16)]~(4+)층간삽입객체음리자CO_3~(2-)화수분자후,주객체문존재착교강적초분자작용력,주요포괄정전화경건작용,차경건작용재수합과정중기주도작용,총체상층판-수(L-W)형,층판-음리자(L-A)형경건강도요강우음리자-수(A-w)형/수-수(W-W)형경건.수착층간수분자적증다,층간거선증대후우초강저.당y=0、1시,객체소재적평면여주체층판평행,차여량층판적거리기본상등;당y=2、3시,객체이편향모일층판적형식존재.여층간H_2O상비,층문음리자CO_3~(2-)대체계태밀도적영향경현저,층판여CO_3~(2-)적총체작용력대우여H_2O적총체작용력.수착수분자수적증가,Mg_3Sn-LDHs-yH_2O체계적축급수합능절대치축점강저,설명Mg_3Sn-LDHs적수합정도불회무한증가,이시구유포화량.
We proposed a periodic interaction model for the magnesium-tin layered double hydroxides,Mg_3Sn-LDHs-yH_2O.Based on density,functional theory,the geometry of Mg_3Sn-LDHs-yH_2O was optimized using the CASTEP program.The distribution of CO_3~(2-) and H_2O in the interlayer and the supermolecular interaction between host and guest was investigated by analyzing the geometric parameters,charge populations,density of states,and stepwise hydration energies.Results showed that when CO_3~(2-) and H_2O were inserted into the layers of[Mg_6Sn_2(OH)_(16)]~(4+),there were strong supermolecular interactions between the host layer and the guests,including hydrogen-bonding and electrostatic interactions.Hydrogen-bonding was superior to the electrostatic interaction in the hydration process.In general,layer-water(L-W)type and layer-anion(L-A)type hydrogen bonding were stronger than anion-water(A-W) type and water-water(W-W)type hydrogen bonding.In Mg_3Sn-LDHs-yH_2O(y=0-3),the interlayer distance increased then decreased slightly with an increase in the number of interlayer water molecules.At y=0 or 1,the plane of CO_3~(2-) and water was parallel to that of the layer and they were approximately in the middle of the two layers.At y=2 or 3,the guests were not parallel to the host layer and their distribution was random.The impact of CO_3~(2-) was more significant than that of H_2O on the density of states of the system.Therefore,the interaction between the layer and CO_3~(2-) was stronger than that between the layer and H_2O.The absolute value for the hydration energy decreased gradually with an increase in the number of water molecules.This indicated that the hydration of Mg_3Sn-LDHs reached a definite saturation state.