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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical investigation of surface reactions of lactic acid on MgO clusters
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Theoretical investigation of surface reactions of lactic acid on MgO clusters

机译：乳酸对氧化镁团簇表面反应的理论研究

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摘要

Interaction of lactic acid with various sizes of magnesium oxide clusters (MgO)_x (x = 2, 4, 6, 8, 9, 12, 15, 16, 18) is investigated. Density functional theory with the PBE functional and a polarized double-ζ basis set is employed to optimize the structures. For MgO dimer, optimizations are also performed at the PBE/DZP, PBE/TZP, and MP2/TZV(d,p) levels of theory, and single-point CCSD(T)/TZV(d,p) calculations are computed at the PBE/TZP optimized geometries. CCSD(T)/TZV(d,p) calculations show that the PBE/DZP results are off by no more than 5 kcal/mol. Dissociative adsorption of a proton bound to oxygen is possible for the carboxylic acid group, the hydroxyl group, and for a simultaneous interaction of the carboxylic acid and hydroxyl groups. Associative adsorption of various functional groups is also possible, although these represent higher energy structures. All of the adsorptions are calculated to be exothermic. Dissociative adsorption of the carboxylic acid group of lactic acid at the lowest coordinated magnesium sites is determined to be the lowest energy structure. Adsorption energies are found to decrease in magnitude as the size of MgO increases. The geometry of the magnesium oxide cluster changes to a nanorod-like structure when lactic acid interacts with higher coordinated magnesium atoms in double layer systems, but remains simple cubic when a third layer is added. The coordination environment rather than the size of the MgO cluster appears to dominate the adsorption energy when the size becomes larger than (MgO)_(12)
机译：研究了乳酸与各种大小的氧化镁簇（MgO）_x（x = 2、4、6、8、9、12、15、16、18）的相互作用。采用具有PBE功能和极化double-ζ基集的密度泛函理论来优化结构。对于MgO二聚体，还在理论水平的PBE / DZP，PBE / TZP和MP2 / TZV（d，p）上执行优化，并且在以下位置计算单点CCSD（T）/ TZV（d，p）计算PBE / TZP优化的几何形状。 CCSD（T）/ TZV（d，p）计算表明，PBE / DZP结果偏差不超过5 kcal / mol。结合于氧的质子的解离吸附对于羧酸基，羟基以及羧酸与羟基的同时相互作用是可能的。各种官能团的缔合吸附也是可能的，尽管这些代表更高的能量结构。计算出所有吸附都是放热的。乳酸的羧酸基团在最低配位镁位点的解离吸附被确定为最低能级结构。随着MgO尺寸的增加，吸附能的大小会降低。当乳酸在双层系统中与较高配位的镁原子相互作用时，氧化镁簇的几何形状变为纳米棒状结构，但在添加第三层时保持简单的立方形状。当尺寸大于（MgO）_（12）时，配位环境而不是MgO簇的大小似乎决定了吸附能。

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