共查询到19条相似文献,搜索用时 760 毫秒
1.
利用高精度从头计算方法研究了H2分子在Al7-阴离子团簇上的吸附及解离过程, 确定了分子吸附及解离吸附的稳定结构,并分析了各结构的光电子能谱. 计算表明H2在Al7-上为弱的物理吸附,吸附能约为0.02 eV;解离过程的能垒约为0.75 eV. 对团簇及解离吸附结构的态密度与实验得到的光电子能谱的比较表明二者能够很好地符合, 确定H2与激光烧蚀产生的团簇直接反应时能在Al7-上发生解离.
关键词:
7-')" href="#">Al7-
2')" href="#">H2
解离吸附
从头计算 相似文献
2.
一个新颖的磷掺杂硼钒氧簇化合物[Li(H2O)2]2[Cu(en)2]3[H2en]2[V12P12B6O68(OH)4(H2O)]·3(H2O)1通过水热法合成,通过Li+连接成一维无限结构,再通过氢键连成三维立体结构。针对该化合物,通过二维红外相关光谱并作了详细分析,化合物1簇阴离子振动偶极矩对磁场和温度的变化均有响应峰,2D-IR COS提供了一种结构表征新方法。 相似文献
3.
4.
5.
6.
管状(MgO)12是(MgO)n的幻数团簇, 非常稳定. 为研究电场对其储氢性能的影响, 本文在B3LYP/6-31G**水平上研究了电场中H2在(MgO)12管状结构上的吸附性质. 结果表明 (MgO)12能承受强电场而保持管状结构并被极化, 其偶极矩增大为场强0.01 a.u. 和0.02 a.u.时的9.21和19.39 deb (1 deb=3.33564×10-30C·m). H2能稳定吸附在单个Mg/O原子上. 无电场时H2在Mg上为侧位吸附, 而在O上为端位吸附; 电场中, H2在Mg和O上均为端位吸附, 且其分子取向沿外电场方向. 由于(MgO)12 及H2均被电场极化, 因此H2在(MgO)12部分位置上的吸附强度显著提高. H2在3配位的Mg/O上的吸附能由无电场时0.08/0.06 eV分别提高到场强为0.01 a.u.和0.02 a.u.时的0.12/0.11 eV 和0.20/0.26 eV. 电子结构分析表明H2吸附在Mg原子上时, 向团簇转移电荷, 电场极化效应是其吸附能较无电场时增大的主要原因. 吸附在O原子上时, 一方面由于O阴离子极化效应更强; 另一方面, H2从(MgO)12得到电荷, 其价轨道与团簇价轨道重叠形成化学键, 因此电场效应更显著. 电场中(MgO)12最多能吸附16个H2, 相应的质量密度为6.25 wt%. 相似文献
7.
给出了优化小分子在团簇表面吸附结构的遗传算法.结合经验势函数,搜寻了水分子在(TiO2)n(n=3—6)团簇上可能的吸附方式;利用B3LYP/6-31G**方法对各种吸附结构进行了优化.结果表明水分子主要通过O原子以非解离方式吸附到团簇中配位数较低或位置比较凸出的Ti原子上.分子轨道分析表明,水分子与团簇之间的成键主要来自吸附位Ti原子3s3p轨道的贡献,水分子的轨道保持了气相水分子中的基本特征,但离域化程度增大
关键词:
2团簇')" href="#">TiO2团簇
2O吸附')" href="#">H2O吸附
遗传算法
DFT 相似文献
8.
利用密度泛函理论(DFT)的B3LYP方法,采用全电子基组6-311+G(d)研究了CuSi6团簇的几何构型和电子结构性质,计算表明CuSi6团簇存在多个能量相近的稳定异构体,且结构中存在多个Cu-Si键,多个低能异构体共存解释了实验中观察到的CuSi6团簇较强的现象.对于CuSi6团簇,计算得到的三个最稳定异构体的垂直电离能,电子亲和能和HOMO-LUMO能隙均相对较大,也表明这三个异构体较为稳定. 相似文献
9.
在传统遗传算法的基础上提出了单母体遗传算法(single-parent genetic algorithm, SPGA),通过对母体团簇实施两种不同的变异操作对结构进行优化,给出了分子团簇结构优化的算法实现. 结合TIP3P模型势函数,研究了水分子团簇(H2O)n(n≤14)的稳定结构. 优化结构和已有理论及实验结果一致. 计算结果表明当n<8时,平均结合能随n增加较快;当n≥8时有小的起伏. n=4,8,10,12的团簇结构具有较高对称性,比较稳定.
关键词:
单母体遗传算法
水分子团簇
结构优化 相似文献
10.
11.
In this article, the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH without and with catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4 and CH3CH2COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H2O, (H2O)2 and (H2O)3)-assisted transition states, as well as different values of pKa for H2SO4, HCOOH and CH3CH2COOH. Very interesting is also the fact that H2SO4-assisted reaction is the most favourable for the hydrogen transfer from HN(NO2)2 to O2NNN(O)OH, due to the smallest pKa (?3.0) value of H2SO4 than H2O, HCOOH, H2SO4 and CH3CH2COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H2SO4-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH, the apparent activation energy of H2SO4-assisted channel also reduces by 9.6 kcal?mol?1, indicating that H2SO4 can affect the isomerisation of HN(NO2)2 to O2NNN(O)OH, most obvious among all the catalysts H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2. 相似文献
12.
The production of hydrogen via steam reforming of ethanol (SRE) is favourable for the use of hydrogen as an alternative fuel. Co–Mo6S8 possesses high activity and stability for SRE to sustainably produce hydrogen. The competition among reaction pathways related to C–H, O–H, C–C, C–O cleavage and H2 formation was studied. The adsorption and reaction of related intermediates in the ESR reaction pathway are described. The results indicated that the most feasible route for the decomposition of ethanol catalysed by Co–Mo6S8 is CH3CH2OH*→CH3CH2O*→CH3CHO*→CH2CHO*→CHCHO*→CHCO*→CH*+CO*. The CH* can be decomposed into C*+H*, and CO* can be oxidised via the redox mechanism of the water gas shift (WGS) reaction. Thus the final products are CO2 and H2. The present result may help people to design an SRE catalyst, which has the ability to break C–C to form CO and H2, then CO react with H2O in the WGS reaction generating CO2 and H2. 相似文献
13.
Despite the fact that B3O is the second simplest B n O radical after BO, a controversy recently emerged concerning the molecular structure of its global minimum. Two recent theoretical groups predicted the linear quartet BBBO to be the ground isomer. By contrast, another recent theoretical group reported that B3O has a doublet B3-ring ground structure. Moreover, larger B n O clusters usually have low-lying B3-ring isomers. In order to determine the accurate energetic competition between linear and cyclic structures in both the doublet and quartet, and to understand the detailed isomerism between various isomers, which is vital for understanding the formation mechanism of B3O, we report the first potential energy surface (PES) study of B3O at various computational levels, including CCSD(T)/6-311+G(2df), CCSD(T)/aug-cc-pVTZ, CCSD(T)/aug-cc-pVQZ and G3B3 for the single-point energy, as well as B3LYP/6-311+G(d) and QCISD/6-311+G(d) for geometrical optimisation. It is shown that the isomers in the quartet state are all thermodynamically more stable than the corresponding doublet ones, and on both the quartet and doublet PESs, the linear form has the lowest energy. Therefore, our study on both linear and cyclic isomers shows that the linear quartet BBBO 4 01 is definitively the ground isomer. Although being much less stable than the quartet linear BBBO global minimum by >20 kcal mol?1, five cyclic isomers exist as local minima, with the bi-cyclic structure 4 02 possessing the smallest barrier of around 15 kcal mol?1. The dissociation energies for direct combination processes B3 + O, B2 + BO and B + B2O are discussed. The present work may be helpful in obtaining a deep understanding of the doping and oxidation process of pure B n clusters. 相似文献
14.
15.
The density functional study of the stabilities,bond characters,static linear polarisabilities,and aromaticities of the ’in-out’ isomerism Hn-60@CnH60(n=70,72,74)
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper uses the density functional theory to analyse the stabilities,bond characters,static linear polarisabilities,and aromaticities of the ’in-out’ isomerism H n-60 @C n H 60 (n=70,72,74).The binding energies,C-H bond energies,and energy gaps explore that the ’in-out’ isometric perhydrogenation of C n (n=70,72,74) can remarkably improve the stabilities.The static linear polarisabilies of H n-60 @C n H 60 (n=70,72,74) are indeed relative to their shapes,while they show almost nonaromatic character.This study can suggest that the ’in-out’ isometric perhydrogenation of fullerenes could lead to the invention of entirely novel potential hydrogen storage nanomaterials. 相似文献
16.
Tianlei Zhang Xinguang Lan Yuhang Zhang Rui Wang Yongqi Zhang Zhangyu Qiao 《Molecular physics》2013,111(4):516-530
ABSTRACTEffects of (H2O)n (n?=?1–3) on the H2O2?+?HO?→?HO2?+?H2O reaction have been investigated by the reactions of H2O2L(H2O)n (n?=?1–3)?+?HO and H2O2?+?HOL(H2O)n (n?=?1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H2O)n (n?=?1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H2O2···H2O?+?HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H2O2···(H2O)2?+?HO (k'(R_WD1)) and H2O2···(H2O)3?+?HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/ktot) is only 0.28% at 240?K, while at high temperature (such as at 425?K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions. 相似文献
17.
S. Vijayakumar 《Molecular physics》2013,111(9):1401-1411
The structures and isomerization process of C3H3NO species have been explored at the MP2/6–311++G(d,p) level of theory of the ab initio method. Eleven minima and four interconversion transition states have been identified. The zero-point vibrational energy corrections were made to predict reliable energies. We predict a five-membered ring-like structure to be the lowest energy isomer, which is 177.73?kcal?mol?1 more stable than the least stable isomer X found on the potential energy surface. The transition states and minima isomers were verified by frequency calculation. Intrinsic reaction coordinate (IRC) calculations have been performed to confirm that each transition state is linked by the desired reactants and products. The isomer stabilities have been studied using the relative energies, chemical hardness and chemical potential. The MHP principle could not predict the order of stability for C3H3NO isomers as arrived at with the relative energies. The role of intramolecular hydrogen bonds on the equilibrium structure has been discussed. The energy barrier and reaction enthalpy have been calculated during isomerization. 相似文献
18.
19.
Dominique Costa Kamal Sharkas Mazharul M. Islam Philippe Marcus 《Surface science》2009,603(16):2484-2493
The reactivity of the (0 0 0 1)-Cr–Cr2O3 surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H2O/nm2 to 14.1H2O/nm2, corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr2O3 surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H2O/nm2), 5 (9.4H2O/nm2) and 6 (14.1H2O/nm2). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H2O/nm2, the Cr–Os (surface oxygen) acid–base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H2O/nm2, molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H2O/nm2, 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are –Cr(OH)2 and –Cr(OH)3– like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr (t2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the –Cr(OH)3-like, –Cr(OH)2 and anhydrous surfaces may be stabilized depending on (T, P) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation. 相似文献