B12Sc4和B12Ti4团簇的储氢性质

提出了两个稳定的团簇B₁₂Sc₄和B₁₂Ti₄, 基于理论计算, 研究了它们的结构与储氢性质. 结果发现, 在这两个稳定的团簇中, 过渡金属原子不会聚合在一起而影响它们对氢气的吸附. B₁₂Sc₄最多可以吸附12个氢分子, 达到7.25% (质量分数)的储氢量. 它的平均每氢分子吸附能量为10.5 kJ·mol^-1. B₁₂Ti₄最多只能吸附8个氢分子, 储氢量为4.78%. 但平均每氢分子吸附能量可达50.2 kJ·mol^-1. 进一步计算表明, 即使在77 K,也需要很高的氢气压力才能使12个氢分子都吸附到B₁₂Sc₄上. 电子结构分析表明, B₁₂Ti₄-nH₂吸附结构中的Kubas作用要大于相应B₁₂Sc₄-nH₂结构中的Kubas作用.     

铁脂质体/水分配系数测定及影响因素考察

基于PAF-301分子模型通过Li 掺杂或B取代等模式设计了几种新型多孔芳香骨架(PAFs)材料, 采用量子力学和分子力学方法对新材料的储氢性能进行研究. 由量子力学计算得到了不同分子片段与H₂之间的结合能, 并结合DDEC方法计算了各分子片段的原子电荷分布. 利用巨正则蒙特卡洛(GCMC)模拟方法计算了77和298 K下H₂在不同PAFs材料中的吸附平衡性质. 结果表明, H₂直接与苯环的结合能较低, 但掺杂Li 原子能够提高H₂与六元环的结合能, 同时Li 原子体现出较高的正电性质, B原子取代苯环中的两个C原子后, 使得原有C原子电负性增强; 77 K下PAF-301Li 具有最高的储氢性能, 而PAF-C₄B₂H₄-Li₂-Si 和PAF-C₄B₂H₄-Li₂-Ge体现出较好的常温储氢性能, 各种材料的常温储氢性能远低于其低温储氢性能. 通过77 K下H₂在PAFs材料中的等位能面分布和吸附平衡质心密度分布对H₂在PAFs 材料中的优先吸附位置进行分析, 发现在PAF-301 和PAF-301Li 骨架中, 由于中心能量较低的等位能区域范围较宽, H₂在其中存在四个明显的吸附高密度分布区域, 而其它三种PAFs晶胞中心能量较低的等位能区域范围较窄, 使得H₂在其中只存在两个明显的吸附高密度分布区域.     

能量最低构型Ca2B4团簇的储氢性能

基于密度泛函理论,研究了Ca₂B₄团簇的几何结构、电子特征和储氢性能。前2个与第4个能量最低构型Ca₂B₄ 01、Ca₂B₄02和Ca₂B₄ 04有很高的热力学稳定性,分别最多可以吸附12、12和10个氢分子,达到16.3%、16.3%和14.0%的储氢量,超过了美国能源部提出的目标(5.5%）。Ca₂B₄ 01(H₂)₁₂、Ca₂B₄ 02(H₂)₁₂和Ca₂B₄ 04(H₂)₁₀的平均每个氢分子吸附能量分别为0.58~4.21 eV、0.54~3.69 eV和0.10~0.12 eV。玻恩-奥本海默分子动力学模拟表明,Ca₂B₄ 01和Ca₂B₄ 02可作为潜在吸附氢气的候选目标,而Ca₂B₄ 04不行。吉布斯自由能校正的氢吸附能结果表明,在101 325 Pa下,Ca₂B₄ 01和Ca₂B₄ 02吸附12个氢气分子有较大的可调节的温度范围。     

N8H8环状异构体的结构与稳定性的理论研究

采用密度泛函理论的B3LYP方法在6-311＋＋G**基组水平上对N₈H₈氮氢环状化合物可能存在的构型进行了几何优化, 得到74种稳定异构体, 应用自然键轨道理论NBO和分子中的原子理论AIM分析了这些化合物成键特征和相对稳定性, G3MP2方法计算了各异构体的能量及生成热. 研究结果表明: N原子孤对电子到相邻的氮氮键的超共轭作用是影响氮氮键长变化的主要因素; N₈H₈环状异构体的稳定性顺序为: 六元环＞七元环＞八元环, 五元环＞三元环＞四元环, 六元环是这些N₈H₈环状异构体中最稳定的, 最不稳定的是四元环, G19是所有环状异构体中能量最低的; M3能量最高, 稳定性最差, A7密度最大.     

簇合物(p-H2)N-HCCCN的结构和能量

采用两体作用势模型和遗传算法对簇合物（p-H₂）_N-HCCCN的极小能量结构和能量进行了理论研究.结果表明,20 个para-H₂分子形成HCCCN周围的第一个溶剂层,第一个溶剂层包含三个溶剂环,每个溶剂环都有6 个para-H₂分子,第19和20个para-H₂分子分别聚集在HCCCN分子的N、H原子末端. 进一步计算了（p-H₂）_N-HCCCN的化学势,发现化学势随para-H₂分子个数的增加呈震荡变化.     

AlmN2和AlmN2＋ (m＝1～8)团簇结构与稳定性的量子化学研究

用密度泛函理论(DFT)的B3LYP方法, 在6-311G*水平上对Al_mN₂和Al_mN₂^＋ (m＝1～8)团簇的几何构型、电子结构、振动频率和分子轨道进行了理论研究. 结果表明, Al_mN₂类团簇的基态结构有两种基本构型, 一种是以N—N键为核心周围与Al原子相配位形成的, 一种是由两个Al_nN (n≤m/2)分子碎片通过共用Al原子或Al—Al键相互结合形成的. 对Al_nN分子碎片相互结合形成结构的绝热电离能讨论得到, m为偶数的团簇比m为奇数的稳定.     

B12Sc4和B12Ti4团簇的储氢性质

提出了两个稳定的团簇B12Sc4和B12Ti4,基于理论计算,研究了它们的结构与储氢性质.结果发现,在这两个稳定的团簇中,过渡金属原子不会聚合在一起而影响它们对氢气的吸附. B12Sc4最多可以吸附12个氢分子,达到7.25%(质量分数)的储氢量,它的平均每氢分子吸附能量为-10.5 kJ·mol-1. B12Ti4最多只能吸附8个氢分子,储氢量为4.78%,但其平均每氢分子吸附能量可达-50.2 kJ·mol-1.进一步计算表明,即使在77 K,也需要很高的氢气压力才能使12个氢分子都吸附到B12Sc4上.电子结构分析表明, B12Ti4-nH2吸附结构中的Kubas作用要大于相应B12Sc4-nH2结构中的Kubas作用     

二维TiC 层表面H2的化学吸附与物理吸附

第一性原理计算研究发现由于二维TiC 单原子层具有高的比表面积与大量的暴露在表面的Ti 原子,其是一种非常有潜力的储氢材料. 计算结果显示H₂可以在二维TiC 单原子层表面进行物理吸附与化学吸附. 其中化学吸附能为每个氢分子0.36 eV,物理吸附能是每个氢分子0.09 eV. 覆盖度为1和1/4层（ML）时,H₂分子在二维TiC 单原子层表面的离解势垒分别为1.12 和0.33 eV. 因此,除了物理吸附与化学吸附,TiC 表面还存在H单原子吸附. 最大的H₂储存率可以达到7.69%（质量分数）. 其中,离解的H原子、化学吸附的H₂、物理吸附的H₂的储存率分别为1.54%、3.07%、3.07%. 符合Kubas吸附特征的储存率为3.07%. 化学吸附能随覆盖度的变化非常小,这有利于H₂分子的吸附与释放.     

N2O+经由B2Пi←X2П跃迁的光解离机理研究

在超声分子束条件下,利用360.50 nm的电离激光使N₂O分子经由[3+1]共振增强多光子电离（REMPI）产生纯净的N₂O⁺（X²Π（000））分子离子,用另一束解离激光在230-275 nm范围扫描获得N₂O⁺经由B²П_i←X²Π跃迁产生的光解碎片（NO⁺和N₂⁺）激发（PHOFEX）谱. 获得的光解碎片激发谱可以归属为B²П_i（00n）←X²Π（000）序列跃迁. 我们分别将线性三原子分子离子N₂O⁺中N―N伸缩振动简化成NO和N之间的简谐振动,N―O伸缩振动简化成N₂和O之间的简谐振动,用谐振子的简谐势能曲线和波函数对N₂O⁺分子离子X²Π和B²П_i电子态振动能级间跃迁的Franck-Condon因子进行计算,和实验得到的碎片离子增强谱实验强度进行比较,对前人给出的分子数据（分子平衡核间距）进行验证,讨论了N₂O⁺经由B²П_i（00n）←X²Π（000）电子态跃迁的光解离机理和碎片离子的分支比.     

14顶点闭合型碳硼烷异构体的结构和稳定性的密度泛函理论研究

采用密度泛函理论(DFT) B3LYP/6-31G(d)方法对14顶点闭合型碳硼烷异构体的几何结构进行优化, 分析了它们的稳定性、电荷分布以及前线分子轨道能级. 结果表明, C₂B₁₂H₁₄碳硼烷的9个异构体都有对应的稳定构型, 并基本保持了B₁₄H₁₄^2－的骨架构型; 除两个C原子取代轴顶点位置B原子的1,14-C₂B₁₂H₁₄外, 其稳定性均随着两个C原子之间距离的增大而增加, 但C原子取代高配位数的B原子不利于其构型的稳定性. 各异构体的负电荷主要分布在C原子上, 同时处于轴向位置的B原子也有部分负电荷, 它们可能成为反应的亲核活性中心. 异构体的HOMO能级的高低与其稳定性相对应, HOMO能级低的异构体稳定性好.     

Hydrogen adsorption on carbon-doped boron nitride nanotube

The adsorption of atomic and molecular hydrogen on carbon-doped boron nitride nanotubes is investigated within the ab initio density functional theory. The binding energy of adsorbed hydrogen on carbon-doped boron nitride nanotube is substantially increased when compared with hydrogen on nondoped nanotube. These results are in agreement with experimental results for boron nitride nanotubes (BNNT) where dangling bonds are present. The atomic hydrogen makes a chemical covalent bond with carbon substitution, while a physisorption occurs for the molecular hydrogen. For the H(2) molecule adsorbed on the top of a carbon atom in a boron site (BNNT + C(B)-H(2)), a donor defect level is present, while for the H(2) molecule adsorbed on the top of a carbon atom in a nitrogen site (BNNT + C(N)-H(2)), an acceptor defect level is present. The binding energies of H(2) molecules absorbed on carbon-doped boron nitride nanotubes are in the optimal range to work as a hydrogen storage medium.     

Theoretical realization of cluster-assembled hydrogen storage materials based on terminated carbon atomic chains

The capacity of carbon atomic chains with different terminations for hydrogen storage is studied using first-principles density functional theory calculations. Unlike the physisorption of H(2) on the H-terminated chain, we show that two Li (Na) atoms each capping one end of the odd- or even-numbered carbon chain can hold ten H(2) molecules with optimal binding energies for room temperature storage. The hybridization of the Li 2p states with the H(2)σ orbitals contributes to the H(2) adsorption. However, the binding mechanism of the H(2) molecules on Na arises only from the polarization interaction between the charged Na atom and the H(2). Interestingly, additional H(2) molecules can be bound to the carbon atoms at the chain ends due to the charge transfer between Li 2s2p (Na 3s) and C 2p states. More importantly, dimerization of these isolated metal-capped chains does not affect the hydrogen binding energy significantly. In addition, a single chain can be stabilized effectively by the C(60) fullerenes termination. With a hydrogen uptake of ～10 wt.% on Li-coated C(60)-C(n)-C(60) (n = 5, 8), the Li(12)C(60)-C(n)-Li(12)C(60) complex, keeping the number of adsorbed H(2) molecules per Li and stabilizing the dispersion of individual Li atoms, can serve as better building blocks of polymers than the (Li(12)C(60))(2) dimer. These findings suggest a new route to design cluster-assembled hydrogen storage materials based on terminated sp carbon chains.     

First-principles study of hydrogen adsorption in metal-doped COF-10

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10 and their interaction with hydrogen molecules. The binding energy of Li atom on COF-10 substrate is found to be about 1.0 eV and each Li atom can adsorb up to three H(2) molecules. However, at high concentration, Li atoms cluster and, consequently, their hydrogen storage capacity is reduced due to steric hindrance between H(2) molecules. On the other hand, due to charge transfer from Li to the substrate, O sites provide additional enhancement for hydrogen adsorption. With increasing concentration of doped metal atoms, the COF-10 substrate provides an additional platform for storing hydrogen. Similar conclusions are reached for Ca doped COF-10.     

金属修饰Ti_2N MXene吸附分解H_2S的第一性原理计算

通过第一性原理计算研究了Ti_2NO_2 MXene对H_2S的吸附、分解行为. Ti_2NO_2对H_2S气体分子的吸附结果表明,两者之间为弱的物理吸附, Ti_2NO_2无法有效吸附H_2S气体.采用过渡金属(Sc、 V)修饰Ti_2NO_2的研究结果表明,Sc和V可以在Ti_2NO_2表面上稳定存在,不易发生团聚,其最稳定吸附位为N原子上方.进一步研究了Sc、 V修饰的Ti_2NO_2对H_2S气体分子的吸附行为,结果表明金属修饰后其吸附H_2S的能力明显提高.此外还发现, H_2S分子可以在Sc/Ti_2NO_2和V/Ti_2NO_2表面直接解离为HS*和H*,而后HS*中的H原子再与H*进一步结合形成H_2, S原子则与过渡金属成键. HS*在V/Ti_2NO_2表面解离的势垒为1.69 eV,低于在Sc/Ti_2NO_2表面的2.08 eV,表明V/Ti_2NO_2有望成为吸附、分解H_2S气体的理想候选材料.     

Adsorption of molecular hydrogen on inorganometallic complexes B<Subscript>2</Subscript>H<Subscript>4</Subscript>M (M=Li,Be, Sc,Ti, V)

Molecular interaction between hydrogen molecules and B₂H₄M (M=Li, Be, Sc, Ti, V) complexes has been studied using the DFT method (M06 functional) and 6-311++G** basis set. The hydrogen uptake capacity of the complexes considered is higher than the target set by the US Department of Energy (5.5 wt% by 2020). The metal atom bound strongly to the B₂H₄ substrate. Adsorption of molecular hydrogen on Be-, Ti-, and V-decorated complexes is thermodynamically possible for all the pressures and temperatures considered whereas it is unfavorable for Li-decorated complexes for all the pressure and temperatures. For the Sc-doped complexes, adsorption of molecular hydrogen is favorable below 330 K and entire pressure range considered. All the H₂ adsorbed complexes are kinetically stable. For all the complexes, the interaction between the inorganometallic complexes and the H₂ molecules adsorbed is attractive whereas that between adsorbed H₂ molecules is repulsive. We have also performed molecular dynamics simulations to confirm the same number of H₂ molecule adsorption from the simulations and DFT calculations.     

H2分子在LaFeO3表面吸附的第一性原理研究

基于密度泛函理论的第一性原理方法,通过计算表面能确定LaFeO₃(010)表面为最稳定的吸附表面,研究了H₂分子在LaFeO₃(010)表面的吸附性质。LaFeO₃(010)表面存在LaO和FeO₂两种终止表面,但吸附主要发生在FeO₂终止表面,由于LaFeO₃(010)表面弛豫的影响,使得凹凸不平的表面层增加了表面原子与H原子的接触面积,表面晶胞的纵向体积增加约2.5%,有利于H原子向晶体内扩散。研究发现,H₂分子在LaFeO₃(010)表面主要存在3种化学吸附方式:第一种吸附发生在O-O桥位,2个H原子分别吸附在2个O原子上,形成2个-OH基,这是最佳吸附位置,此时H原子与表面O原子的作用主要是H1s与O2p轨道杂化作用的结果,H-O之间为典型的共价键。H₂分子的解离能垒为1.542 eV,说明表面需要一定的热条件,H₂分子才会发生解离吸附;第二种吸附发生在Fe-O桥位,1个H原子吸附在O原子上形成1个-OH基,另一个H原子吸附在Fe原子上形成金属键;第三种吸附发生在O顶位,2个H原子吸附在同一个O原子上,形成H₂O分子,此时H₂O分子与表面形成物理吸附,H₂O分子逃离表面后容易形成氧空位。此外,H₂分子在LaFeO₃(010)表面还可以发生物理吸附。     

First principle study of hydrogen storage on the graphene-like aluminum nitride nanosheet

Employing density functional calculations including an empirical dispersion term, we investigated the hydrogenation of an aluminum nitride nanosheet (h-AlN) with atomic and molecular hydrogen. It was found that atomic H prefers to be adsorbed on an N atom rather than Al, releasing energy of 21.1 kcal/mol. The HOMO/LUMO energy gap of the sheet is dramatically reduced from 107.9 to 44.5 kcal/mol, upon the adsorption of one hydrogen atom. The adsorption of atomic H on the h-AlN presents properties which are promising for nanoelectronic applications. The molecular H₂ was found to be adsorbed collinearly on an N atom and dissociated to two H atoms on Al–N bond. Calculated barrier and adsorption energies for this dissociation process are about +18.9 and ?1.9 kcal/mol. We predict that each nitrogen atom in an AlN sheet can adsorb two hydrogen molecules on opposite sides of the sheet, and thus the gravimetric density for hydrogen storage on AlN sheet is evaluated to be about 8.9 wt%.     

Study of H2O and HOCH2CH2OH Adsorption on the Relaxation Surface of β-Si3N4（0001） by Density Functional Theory

Density functional theory （DFT） B3LYP method is used to theoretically investigate the adsorption conformations of H2O and glycol on the relaxation surface of β-Si3N4（0001） with cluster models. For H2O, the most stable structure is that adsorbed through the H atom lying above a N（3） site of the relaxation surface of β-Si3N4（0001）; while for glycol, it is the one adsorbed via the H atom lying above the center of Si（2） and N（3） of the same relaxation surface. The adsorption energy, adsorption bond and transfer electrons of the two adsorbed substances prove that glycol is easy to be adsorbed on the relaxation surface of β-Si3N4（0001）.     

Study of H2O and HOCH2CH2OH Adsorption on the Relaxation Surface of β-Si3N4(0001) by Density Functional Theory

Density functional theory (DFT) B3LYP method is used to theoretically investigate the adsorption conformations of H2O and glycol on the relaxation surface of β-Si3N4(0001) with cluster models. For H2O, the most stable structure is that adsorbed through the H atom lying above a N(3) site of the relaxation surface of β-Si3N4(0001); while for glycol, it is the one adsorbed via the H atom lying above the center of Si(2) and N(3) of the same relaxation surface. The adsorption energy, adsorption bond and transfer electrons of the two adsorbed substances prove that glycol is easy to be adsorbed on the relaxation surface of β-Si3N4(0001).