Ionization Dynamics of the Small-Sized Water Clusters: A Direct Ab Initio Trajectory Study †
Ionization Dynamics of the Small-Sized Water Clusters: A Direct Ab Initio Trajectory Study †
复制标题
DOI：
10.1021/jp049269l
复制
发表时间：
2004-07
影响因子：
2.9
通讯作者：
H. Tachikawa
中科院分区：
文献类型：
--
作者：
H. Tachikawa
用全维直接从头算轨道方法研究了水分子团簇（H2O）n（n = 3-6）的电离动力学.在HF/6- 311 G（d，p）和B3 LYP/6- 311 G（d，p）水平上进行了静态从头算和密度泛函理论计算，在HF/6-31 G（d）和6-311 G（d，p）水平上进行了直接从头算轨道计算.静态从头算和密度泛函理论计算表明，在所有情况下（n = 3-6），最稳定的结构是环状结构。在水三聚体的电离过程中，生成了（H3 O + OH）H2O络合物（络合物形成通道）.在较大的团簇中（n = 4-6），只有在（H2O）n电离后才出现OH解离（OH解离通道）。OH的解离分两步进行：第一步是H2 O +沿团簇中的氢键沿着向H2 O转移，然后形成（H3 O + OH）络合物，其结构式为（H2 O +）-H2 O-H2 O →（OH）（H3 O +）-H2 O.第二步是从H3 O + OH到邻近水分子的第二个质子转移过程，表示为（OH）-H3 O + -H2 O →（OH）-H2 O-H3 O +。发现OH解离在第二次质子转移后立即发生。中间配合物的寿命分布在50-200 fs的范围内，n = 4-6。根据理论结果对反应机理进行了讨论。
The ionization dynamics of the water clusters (H 2 O) n (n = 3-6) have been investigated by means of the full-dimensional direct ab initio trajectory method. The static ab initio and DFT calculations were carried out at the HF/6-311G(d,p) and B3LYP/6-311G(d,p) levels, whereas the direct ab initio trajectory calculations were performed at the HF/6-31 G(d) and 6-311 G(d,p) levels of theory. The static ab initio and DFT calculations showed that the most stable structure is the cyclic form for all cases (n = 3-6). In the ionization of the water trimer, the complex (H 3 O + OH)H 2 O was obtained as a product (complex formation channel). In the larger clusters (n = 4-6), the OH dissociation was only found after the ionization of (H 2 O) n (OH dissociation channel). The OH dissociation occurs via two-step processes: the first step is a proton-transfer process from H 2 O + to H 2 O along the hydrogen bond in the cluster, and then the (H 3 O + OH) complex is formed as a core in the cluster, expressed by (H 2 O + )-H 2 O-H 2 O → (OH)(H 3 O + )-H 2 O. The next step is the second proton-transfer process from H 3 O + OH to the neighboring water molecule, which is expressed by (OH)-H 3 O + -H 2 O → (OH)-H 2 O-H 3 O + . It was found that the OH dissociation takes place immediately after the second proton transfer. The lifetimes of the intermediate complexes are distributed in the range 50-200 fs for n = 4-6. The reaction mechanism was discussed on the basis of theoretical results.