CO在Cu(100)表面最佳吸附位研究

采用密度泛函理论(DFT)对CO分子在Cu(100)表面上的吸附行为进行了研究。计算结果表明：顶位吸附和桥位吸附这两种模型中CO分子都倾斜地吸附在Cu原子上，其中顶位吸附的C-0键长(0．1155nm)和Cu—C键长(0．1840nm)与实验值符合得很好，而且C-O键长均比自由CO分子的C-O键长要长。说明Cu原子活化了CO分子。另外，顶位吸附时的体系能量较低，且有较大的吸附能，说明顶位吸附模型更稳定，所以CO很可能采用顶位吸附模型。从Mulliken轨道分布数据可以看出Cu原子上的σ电子向Cu原子的4p轨道和O原子的2p轨道转移，从而CO分子上的电子云会发生重排，组成新的轨道，所以CuCO就会形成弯曲结构。     

甲醛在CeO_2(110)表面的吸附

利用密度泛函理论计算了甲醛在洁净CeO_2(110)表面的吸附行为,发现甲醛在表面存在化学与物理吸附。甲醛化学吸附时,甲醛的碳、氧原子分别与表面氧、铈原子发生作用,生成CH_2O_2,平面结构变为四面体构型;吸附能随覆盖度的减小而增大;电子结构分析表明,其最高占据轨道nO的电子进入表面铈原子的空轨道,形成Ce-Os化学键;而表面氧原子的电子填充到甲醛的C-Of反键轨道,形成新的C-Os键,甲醛的C-Of键长伸长。而物理吸附的甲醛,平面结构不变,吸附能较小,电子结构无明显变化。     

甲醇在金红石型TiO_2(110)表面的吸附解离

金红石型二氧化钛在光催化中有许多应用。运用周期性密度泛函理论计算方法研究了甲醇在金红石型二氧化钛(110)表面的吸附和解离方式。分别考察了饱和固定和饱和放开模型上甲醇的吸附、解离及解离过程中过渡态能垒的情况。通过对计算能量和能垒、解离前后各键长的分析比较,得出结论:在金红石型二氧化钛(110)表面上,甲醇的分子吸附形式和解离吸附形式能够同时存在,但是解离吸附的存在形式略为稳定。     

SCR反应过程中NO/NH3在γ-Al2O3表面吸附特性

采用密度泛函理论（DFT）方法研究了NO和NH₃在完整和有缺陷的γ-Al₂O₃（110）表面吸附与SCR（选择催化还原）反应特性。研究表明,NO在完整的（110）表面的吸附作用较弱,而NH₃分子的吸附作用较强,NH₃分子在Al原子顶位可形成稳定吸附。反应路径研究结果表明完整的（110）表面上SCR反应的决速步为-NH₂NO基团的分解,反应的最大能垒为235.75 kJ·mol^-1。对于产生氧空穴的有缺陷（110）表面,NO和NH₃均可稳定吸附,NH₃在吸附过程中可直接裂解成NH₂和H。另外,SCR反应在有缺陷（110）表面的最大能垒明显较低,说明氧空穴的存在促进了SCR脱硝反应的进行。     

N_2O在Rh(100)表面吸附机理的量子化学研究

在对三效催化剂(TWC)表面N2O的催化反应实验及理论研究的基础上,选用了在过渡金属催化体系量子化学理论研究中常用的密度泛函方法,采用CASTEP计算程序,交换相关函数采用PW91函数,计算了N2O在催化剂Rh(100)面上的化学吸附。计算结果显示:通过对N端吸附位和O端吸附位的N-N、N-O、Rh-N、Rh-O等键长和吸附能的比较,说明NO最有可能发生的是N端顶位吸附。     

密度泛函理论研究NO在CuO(111)的表面吸附

为了深入研究纳米CuO与含能材料分解产生的NO间的相互作用,采用密度泛函理论研究了NO在CuO(1 1 1)表面的吸附行为,同时在NO吸附的最稳定位点研究NO_2在Cu表面的吸附及其对NO的影响;通过DMol~3模块中广义梯度密度泛函理论(GGA)的Perdew-Burke-Ernzerh (PBE)方法对吸附构型进行了计算。结果表明,NO以分子形式吸附在CuO(1 1 1)表面,较为稳定的吸附构型为NO的N原子与CuO表面的Cu、O原子相互作用,均为化学吸附;最稳定的吸附构型为NO吸附在Cu1位点上,吸附能为-0.89eV;HOMO-LUMO轨道能隙值和态密度图分析均表明NO和CuO表面有强烈相互作用;Mulliken电荷布局分析显示,电荷从NO转移到Cu表面,NO带部分正电荷;在含能材料分解过程中,NO气体稳定吸附在CuO表面,但当存在NO_2时,NO的吸附位点可能会被吸附能力更强的NO_2占据。     

CO2在La2O3(011)表面吸附和活化的DFT计算

运用广义梯度密度泛函理论方法(density functional theory,DFT),结合周期性平板模型,研究了CO2在La2O3(011)表面的吸附和活化,计算了CO2吸附的吸附能和Mulliken电荷数.结果表明,CO2在La2O3(011)表面吸附形成6种平衡构型,分别为CO2-η1、CO2-η2、CO2-...     

NiM双金属和γ-Al2O3的相互作用及对CO2吸附的影响

用密度泛函理论(DFT)研究了单金属Ni2及NiMn,NiFe,NiCo和NiCu四种双金属与γ-Al2O3之间的相互作用及其对CO2吸附的影响.通过计算NiM在MgO上结合能、电子结构以及CO2在NiM/γ-Al2O3上的吸附能发现:NiM和γ-Al2O3之间的作用是电子的,NiM和γ-Al2O3之间电子的转移数以及NiM的d-带中心的变化能表现了NiM和γ-Al2O3之间相互作用的强弱;NiM和γ-Al2O3之间相互作用的强弱直接影响催化剂对CO2的吸附能力,相互作用越强,CO2的吸附越强;除了NiCu/γ-Al2O3,其他三种负载型双金属对CO2的吸附能力均强于负载的单金属Ni催化剂,其中,NiFe/γ-Al2O3对CO2的吸附能力最强.     

十八胺与混合胺在氯化钾晶体表面选择性吸附的量化计算

氯化钾是我国主要的农业用肥,主要通过正浮选法从盐湖卤水中分离提取,浮选过程中起核心作用的是捕收剂。但在以传统的十八胺为捕收剂生产氯化钾时,低温下的浮选收率较低;而以混合胺为捕收剂时,低温下的浮选收率明显提高。为了解释混合胺的作用机理,研究了十八胺和混合胺在KCl和NaCl晶体表面的相互作用。通过表面能的计算确定稳定晶面的厚度及晶面结构,计算了H₂O分子和捕收剂在KCl和NaCl晶体表面的吸附能,结果表明：相对于NaCl,十八胺更易在KCl晶体表面发生吸附,混合胺有着对KCl更强的吸附能力;混合胺捕收剂在KCl晶体表面的吸附能小于ODA⁺离子在KCl晶体表面的吸附能,这是由于混合胺中二十胺的加入使捕收剂的疏水基碳链长度增加,提高了捕收剂分子在晶体表面吸附后的表面疏水性;而十二胺的加入则发挥了类似起泡剂的作用,改善了捕收剂在KCl饱和溶液中的分散状态,3种胺之间产生了协同效应,提高了捕收剂对KCl的吸附能力。     

Study of H2O adsorption on sulfides surfaces and thermokinetic analysis

Adsorption of water on mineral surfaces was studied using density functional theory and microcalorimetry technique. The calculation results show that galena and molybdenite are hydrophobic, while pyrite and sphalerite is hydrophilic. Thermokinetic analysis shows that the heat of adsorption is in decreasing order of pyrite, sphalerite, galena and molybdenite, which is in good agreement with the calculation results. The adsorption kinetics parameters of hydrophobic galena and molybdenite surfaces are close, while those of hydrophilic pyrite and sphalerite surfaces are very different. The adsorption rate of water on the sphalerite surface is larger than that of water on the pyrite surface.     

Molecular and dissociative adsorption of a single water molecule on a β‐dicalcium silicate (100) surface explored by a DFT approach

The adsorption of water on a C₂S surface initiates belite to hydrate. In the present work, the adsorption behavior of single water molecule on a β‐C₂S (100) surface is explored using density functional theory (DFT) due to the lack of alternative approaches for direct observation. Four possible calcium atom sites on the β‐C₂S (100) surface slab are considered in our calculations. The results show that water can adsorb on the 2 five‐coordinated calcium sites only via molecular adsorption with adsorption energies of 0.59 and 0.85 eV, respectively, but can dissociate on the other 2 six‐coordinated calcium sites with higher adsorption energies of 0.96 and 0.99 eV, respectively. The energy barriers to the dissociative adsorption of water at the Ca(III) site(0.10 eV) is much lower than that at the Ca(IV) site, indicating that water prefers to adsorb and dissociate on Ca(III) sites. The dissociative adsorption of water causes more obvious surface calcium shifts and Si–O bond length increases than molecular adsorption. The dissociative adsorption of a water molecule changes the electron distribution, and the overlap between Ca 2p and O 2s orbitals leads to new Ca–O bond formations.     

吡啶类缓蚀剂及其在Al(111)表面吸附行为的密度泛函理论分析

利用密度泛函理论方法研究了3种吡啶类缓蚀剂分子(吡啶、3-甲基吡啶和4-甲基吡啶)的反应活性及溶剂条件下在Al(111)表面的吸附行为。分子反应活性的量化计算结果表明,3种缓蚀剂分子的前线轨道均分布在吡啶环上,亲核和亲电活性中心均位于吡啶环的N原子上。分子与Al表面吸附的量化计算结果表明,3种分子均能与Al(111)面发生化学吸附,吸附强度顺序与实验测得的缓蚀效率顺序相一致,且缓蚀剂分子与Al(111)面的相互作用是由成键原子的轨道杂化所致。此外,3-甲基吡啶和4-甲基吡啶两个分子还能平行于Al(111)面发生物理吸附。     

氮掺杂Stone-Wales缺陷石墨烯吸附H2S的密度泛函理论研究

利用密度泛函理论研究H₂S分子在氮掺杂Stone-Wales（SW）缺陷石墨烯上的吸附行为,通过吸附能、差分电荷密度、Bader电荷和电子态密度等分析了H₂S分子在SW缺陷石墨烯及氮掺杂SW缺陷石墨烯上的吸附差异。计算结果表明氮原子掺杂可以有效提升H₂S分子与石墨烯表面的相互作用,并加强二者之间的电荷转移。其中,氮原子主要作为电子传递的桥梁参与H₂S与石墨烯表面之间的电荷转移。H₂S分子被选择性吸附在SW缺陷及氮掺杂SW缺陷石墨烯的五元碳环中心处,这说明五元碳环的电荷分布促进H₂S分子的吸附行为。     

Mechanism of methanol decomposition on the Pd/WC(0001) surface unveiled by first-principles calculations

In this study, the decomposition of methanol into the CO and H species on the Pd/tungsten carbide (WC)(0001) surface is systematically investigated using periodic density functional theory (DFT) calculations. The possible reaction pathways and intermediates are determined. The results reveal that saturated molecules, i.e., methanol and formaldehyde, adsorb weakly on the Pd/ WC(0001) surface. Both CO and H prefer three-fold sites, with adsorption energies of −1.51 and −2.67 eV, respectively. On the other hand, CH₃O stably binds at three-fold and bridge sites, with an adsorption energy of −2.58 eV. However, most of the other intermediates tend to adsorb to the surface with the carbon and oxygen atoms in their sp³ and hydroxyl-like configurations, respectively. Hence, the C atom of CH₂OH preferentially attaches to the top sites, CHOH and CH₂O adsorb at the bridge sites, while COH and CHO occupy the three-fold sites. The DFT calculations indicate that the rupture of the initial C–H bond promotes the decomposition of CH₃OH and CH₂OH, whereas in the case of CHOH, O–H bond scission is favored over the C–H bond rupture. Thus, the most probable methanol decomposition pathway on the Pd/WC(0001) surface is CH₃OH → CH₂OH → trans-CHOH → CHO → CO. The present study demonstrates that the synergistic effect of WC (as carrier) and Pd (as catalyst) alters the CH₃OH decomposition pathway and reduces the noble metal utilization.     

BrONO_2与Br(~2P_(3/2))气相反应的密度泛函理论研究

采用密度泛函理论计算方法B3LYP和基组6 31G(d),对BrONO2+Br(2P3/2)的反应机理进行了理论计算,得到各种可能反应途径的过渡态,并经过频率振动分析和内禀反应坐标(IRC)分析加以确认。结果表明:该反应是3通道反应,其中BrONO2+Br→Br2+NO3的反应活化能(5.25kJ/mol)最低,是反应主通道。     

The adsorption of methyl nitrite on the Au(111) surface

The interaction of the methyl nitrite molecule (CH₃ONO) with the gold(111) surface has been studied by means of density functional calculations. The perfect Au(111) surface has been represented by a rather large cluster model, Au₂₂, that was in turn used to extract information about the preferred adsorption geometry of the CH₃ONO species. Vibrational frequencies and adsorption energy are also reported. The calculated adsorption energies are 31.2 kJ/mol with respect to gas phase cis-conformer and 35.1 kJ/mol with respect to trans-methyl nitrite, very close to the experimental adsorption energy of 33.5 kJ/mol. From the analysis of vibrational frequencies of gas phase and adsorbed species it is concluded that only the cis-conformer is present at the Au(111) surface.     

PP/AlN复合材料导热机理研究

以氮化铝(AlN)粉末、聚丙烯(PP)为原料,通过共混-模压法制备了PP/AlN导热复合材料,并对其导热性能进行检测。研究发现,该复合材料的导热系数与AlN添加量之间不是线性关系而是呈幂函数关系,与介电逾渗理论基本吻合。根据检测数据并参考介电逾渗理论,提出了导热逾渗模型,并利用该模型和其他导热预测模型对PP/AlN复合材料的导热系数进行了计算。结果表明:复合材料的导热系数随AlN质量分数的增加呈幂函数增加趋势;实际检测结果与导热逾渗模型的预测结果基本相符,使该理论得到了验证。