A DFT study of H2 dissociation on a series of Mo x S y clusters was performed, including homolytic and heterolytic dissociation. The preference for the two pathways on these models show much difference, as the Mo coor...A DFT study of H2 dissociation on a series of Mo x S y clusters was performed, including homolytic and heterolytic dissociation. The preference for the two pathways on these models show much difference, as the Mo coordination number increases, the homolytic dissociation becomes easier, whereas the heterolytic dissociation becomes more difficult. Furthermore, frontier orbital theory was used to analyze the dissociation mechanisms of these two pathways. It was found that the symmetry and energy gap of Mo x S y's HOMO and H2's LUMO are the decisive factors in H2 activation.展开更多
为探究抗氧剂抗氧化活性,采用Materials Studio 7. 0版本模拟软件Dmol3模块对自由基捕捉剂类抗氧剂中的酚类和胺类抗氧剂分子进行模拟计算分析。通过对4种典型抗氧剂分子的前线轨道及X—H键解离能结果进行分析可知,2,6-二叔丁基对甲酚...为探究抗氧剂抗氧化活性,采用Materials Studio 7. 0版本模拟软件Dmol3模块对自由基捕捉剂类抗氧剂中的酚类和胺类抗氧剂分子进行模拟计算分析。通过对4种典型抗氧剂分子的前线轨道及X—H键解离能结果进行分析可知,2,6-二叔丁基对甲酚抗氧化活性略好于4,4亚甲基双(2,6-二叔丁基苯酚),N-苯基-α-萘胺抗氧化活性明显高于4-丁基-4’-辛基二苯胺,且在此4种抗氧剂中酚类抗氧剂活性略高于胺类。在典型抗氧剂分子的基础上,探究取代基变化对分子抗氧化活性的影响,得出取代基对分子的抗氧化活性有显著影响、且取代基碳数越多抗氧剂分子越活泼的结论。展开更多
During the precipitation of gibbsite from supersaturated sodium aluminate solution, the main aluminum containing species in solution will transform from tetrahedral [Al(OH) 4] - to sixfold octahedral [(H 2O) 2Al (OH) ...During the precipitation of gibbsite from supersaturated sodium aluminate solution, the main aluminum containing species in solution will transform from tetrahedral [Al(OH) 4] - to sixfold octahedral [(H 2O) 2Al (OH) 4] -. In order to elucidate the mechanisms responsible for above transformation, the formation Gibbs free energy as well as frontier orbits of a wide range of aluminum species are studied by ab initio method at B3LYP/6 31G** level. Based on theoretical calculation results, thermodynamic possibility and coordination possibility for aluminate ion transforming from [Al(OH) 4] - to [(H 2O) 2Al(OH) 4] - are analyzed and thermodynamic permitted reaction pathways are extracted. It is found that [Al(OH) 4] - can not react directly with H 2O to carry out the variation of coordination number. Transformation of tetrahedral [Al(OH) 4] - to octahedral [(H 2O) 2Al(OH) 4] - is involved in two reaction pathways, one is realized by neutral [Na(H 2O) + 4·Al(OH) - 4] acting mediator, the other is carried by neutral [(H 2O)Al(OH) 3]. Though there is a strong thermodynamic trend for the transformation of [Al(OH) 4] - to [(H 2O) 2Al(OH) 4] -, the practical transformation is very slow. Thus, it can be concluded that there is a great kinetic resistance during the transformation from [Al(OH) 4] - to [(H 2O) 2Al(OH) 4] -.展开更多
基金the funding by the State Key Project (Grant Nos. 2012CB224802 and 2012BAE05B03)by the Technology Development Project of SINOPEC (S112101)
文摘A DFT study of H2 dissociation on a series of Mo x S y clusters was performed, including homolytic and heterolytic dissociation. The preference for the two pathways on these models show much difference, as the Mo coordination number increases, the homolytic dissociation becomes easier, whereas the heterolytic dissociation becomes more difficult. Furthermore, frontier orbital theory was used to analyze the dissociation mechanisms of these two pathways. It was found that the symmetry and energy gap of Mo x S y's HOMO and H2's LUMO are the decisive factors in H2 activation.
文摘为探究抗氧剂抗氧化活性,采用Materials Studio 7. 0版本模拟软件Dmol3模块对自由基捕捉剂类抗氧剂中的酚类和胺类抗氧剂分子进行模拟计算分析。通过对4种典型抗氧剂分子的前线轨道及X—H键解离能结果进行分析可知,2,6-二叔丁基对甲酚抗氧化活性略好于4,4亚甲基双(2,6-二叔丁基苯酚),N-苯基-α-萘胺抗氧化活性明显高于4-丁基-4’-辛基二苯胺,且在此4种抗氧剂中酚类抗氧剂活性略高于胺类。在典型抗氧剂分子的基础上,探究取代基变化对分子抗氧化活性的影响,得出取代基对分子的抗氧化活性有显著影响、且取代基碳数越多抗氧剂分子越活泼的结论。
文摘During the precipitation of gibbsite from supersaturated sodium aluminate solution, the main aluminum containing species in solution will transform from tetrahedral [Al(OH) 4] - to sixfold octahedral [(H 2O) 2Al (OH) 4] -. In order to elucidate the mechanisms responsible for above transformation, the formation Gibbs free energy as well as frontier orbits of a wide range of aluminum species are studied by ab initio method at B3LYP/6 31G** level. Based on theoretical calculation results, thermodynamic possibility and coordination possibility for aluminate ion transforming from [Al(OH) 4] - to [(H 2O) 2Al(OH) 4] - are analyzed and thermodynamic permitted reaction pathways are extracted. It is found that [Al(OH) 4] - can not react directly with H 2O to carry out the variation of coordination number. Transformation of tetrahedral [Al(OH) 4] - to octahedral [(H 2O) 2Al(OH) 4] - is involved in two reaction pathways, one is realized by neutral [Na(H 2O) + 4·Al(OH) - 4] acting mediator, the other is carried by neutral [(H 2O)Al(OH) 3]. Though there is a strong thermodynamic trend for the transformation of [Al(OH) 4] - to [(H 2O) 2Al(OH) 4] -, the practical transformation is very slow. Thus, it can be concluded that there is a great kinetic resistance during the transformation from [Al(OH) 4] - to [(H 2O) 2Al(OH) 4] -.
