内嵌富勒烯[M@C70] (M=Li, Na, K, Be, Mg, Ca)与[Mg(H2O)6]2+相互作用的密度泛函理论研究

使用密度泛函理论方法, 对内嵌多种碱金属及碱土金属原子(M=Li, Na, K, Be, Mg, Ca)的富勒烯C70与水合Mg(II)离子之间的相互作用进行了理论研究. 首先对各原子(M=Li, Na, K, Be, Mg, Ca)嵌入C70后的形成能进行了讨论, 之后计算了[M@C70]各体系与[Mg(H2O)6]2+的相互作用能, 并采用自然键轨道理论(NBO)研究了电荷转移的情况, 最后进行了电子密度拓扑分析. 结果表明, 内嵌原子半径越大, [M@C70]各体系的热力学稳定性就越高, 转移至[Mg(H2O)6]2+的电荷也随之增加, 二者之间的相互作用属于闭壳层相互作用及共价作用.     

MC20F20(M=Li,Na,Be和Mg)几何结构和电子性质的密度泛函计算研究

采用密度泛函理论(density functional theory, DFT)中的广义梯度近似(generalized gradient approximation, GGA)对MC20F20(M=Li,Na,Be和Mg)的几何结构和电子性质进行了计算研究.几何结构研发现:随着内掺原子序数的增加,金属原子M对C20F20中的C-C键的影响越来越大,而对C-F键的影响甚微.掺杂能计算表明:MC20F20的掺杂能均为负值,需要在一定的实验条件下才能被合成.内掺碱金属和碱土金属分别产生了两类截然不同的能隙和磁性.其中,内掺碱金属的能隙非常小,且带有1μB的净磁矩,表现出磁性;而内掺碱土金属的能隙比C60的能隙还大,净自旋为0,表现出非磁性.     

(XB2)2(X=Al, Be, Na, Mg)团簇结构与性质的密度泛函研究

用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G·基组水平上对(XB2)2(X=Al,Be,Na, Mg)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的电子结构、振动特性、成键特性和电荷特性等进行了理论研究.结果表明,团簇的几何结构大多是平面结构,通常是B-B键和B-X键共存,较少出现X-X键.团簇的稳定结构中通常是几个呈负电性的B原子形成一个负电中心,而其他B原子和X原子处在端位,且显正电性.     

NH3与MH(M=Li,Na)反应机理的密度泛函理论研究

采用密度泛函理论B3LYP方法研究了NH3与MH(M=Li,Na)的放氢反应机理,在6-311G(2d,2p)基组水平上对反应物、中间体、过渡态及产物进行了全几何参数优化,频率分析和内禀反应坐标(IRC)计算证实了中间体和过渡态的正确性和相互连接关系。计算结果表明,NH3与MH(M=Li,Na)的反应均为单通道的氢取代反应,反应生成LiNH2(NaNH2)与H2。     

(XB2)2(X=Al, Be, Na, Mg)团簇的密度泛函研究

用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对(XB2)2(X=Al,Be,Na,Mg)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的电子结构、振动特性、成键特性和电荷特性等进行了理论研究.结果表明,团簇的几何结构大多是平面结构,通常是B-B键和B-X键共存,较少出现X-X键.团簇的稳定结构中通常是几个呈负电性的B原子形成一个负电中心,而其他B原子和X原子处在端位,且显正电性.     

M@C_(20)H_(20)(M=Sc,V,Cr,Mn,Fe,Co,Ni)几何结构和电子性质的理论研究

采用密度泛函理论(DFT)中的广义梯度近似(GGA)方法对M@C_(20)H_(20)(M=Sc,V,Cr,Mn,Fe,Co,Ni)几何结构和电子性质进行了计算研究.几何结构优化发现,过渡金属原子M内掺到C_(20)H_(20)笼时,都稳定于碳笼中心.能隙和内掺能计算发现,M@C_(20)H_(20)的热力学稳定性随着M原子序数的增大而逐渐减弱,内掺M原子使得其动力学稳定性大幅度下降,但是其中Ni@C_(20)H_(20)结构仍然具有良好的热力学和动力学稳定性,其有望在实验中被成功合成出来.电子性质研究发现,随着M原子序数的逐渐增大,M原子对M@C_(20)H_(20)前线轨道的贡献也越来越大,M@C_(20)H_(20)(M=Sc,V,Cr,Mn,Fe,Co)都具有一定的磁矩,而Ni@C_(20)H_(20)为闭壳层结构,磁矩为零.     

金属原子(Li,Na,K,Rb,Be,Mg,Ca,Sr,Ba)与金富勒烯混合纳米团簇的研究

运用密度泛函理论,对金属原子(Li,Na,K,Rb,Be,Mg,Ca,Sr,Ba)与金富勒烯混合纳米团簇的结构和性质进行了详细研究.在研究结果中,发现了Au31Ba纳米材料,结构比金富勒烯还要稳定,又具有较高的化学活性,可以用来做优良的催化剂.     

第一主族元素(Li,Na,K)和第二主族元素(Be,Mg,Ca)掺杂二维六方氮化硼单层的第一性原理计算研究

采用基于密度泛函理论的第一性原理计算方法研究了第一、第二主族元素取代六方BN单层中的B的几何结构、磁性性质和电子结构.研究发现,掺杂的BN单层出现明显的自旋极化特性.对Li,Na,K而言,掺杂后超胞的总磁矩为2μB,对Mg,Ca而言,超胞的总磁矩为1μB,磁矩主要局域在与杂质原子最近邻的N原子上.而对于Be,超胞的总磁矩为0.705μB,磁矩分散在所有的N原子上.对于6种掺杂情况,给出了相应的自旋密度图.掺杂体系产生明显的杂质能级,给出了总态密度和局域投影态密度等结果,分析了杂质能级的产生.发现Mg和Ca掺杂体系的态密度具有明显的半金属特性.     

密度泛函理论计算内掺富勒烯M@C60H60(M=Li、Na)的几何结构和电子性质

采用密度泛函理论中的广义梯度近似(generalized gradient approximation,简称GGA),对M@C_(60)H_(60) (M=Li、Na)几何结构和电子性质进行计算研究.发现M原子的平衡位置处在偏心位置处,并且稳定的存在于一个围绕中心的球体内;掺杂能计算表明:M@C_(60)H_(60)需要在一定的实验条件下才能被合成出来;电子性质分析表明:M原子掺入到C_(60)H_(60)中,对费米能级附近有一定贡献,并产生了1 μB的净磁矩.     

硝酸羟胺-(H_2O)_n复合物氢键相互作用的密度泛函研究

为研究硝酸羟胺-(H_2O)_n复合物的氢键作用,采用密度泛函B3LYP方法在6-311++G(d, p)基组水平上对硝酸羟胺-(H_2O)_n复合物的结构进行优化,采用MP2/6-311++G(d, p)方法,经基组叠加误差和零点能校正计算得到复合物的相互作用能.利用自然键轨道分析方法研究复合物氢键作用的本质,并对复合物中水分子的振动光谱进行分析.计算结果表明,硝酸羟胺-(H_2O)_n复合物存在着6个硝酸羟胺-H_2O稳定构型和8个硝酸羟胺-(H_2O)_2稳定构型,且最稳定构型的相互作用能分别为52.821 kJ·mol~(-1)和73.349 kJ·mol~(-1).在硝酸羟胺-(H_2O)_n复合物中,水中H-O伸缩振动频率明显红移,且红移增大的程度与复合物稳定化能的变化趋势基本一致.     

Interaction studies of cysteine with Li+, Na+, K+, Be2+, Mg2+, and Ca2+ metal cation complexes

The coordination geometries, electronic features, metal ion affinities, entropies, and the energetics of Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, and Ca²⁺ metal cations with different possible conformations of cysteine complexes were studied. The complexes were optimized using density functional theory (B3LYP) and second order Moller–Plesset Perturbation (MP2) theory methods using 6‐311 + +G** basis set. The interactions of the metal cations at different nucleophilic sites of cysteine conformations were considered after a careful selection among several binding sites. All the metal cations coordinate with cysteine in a tridentate manner and also the most preferred position for the interaction. It is found that, the overall structural parameters of cysteine are not altered by metal ion substitution, but, the metal ion‐binding site has undergone a noticeable change. All the complexes were characterized by an electrostatic interaction between ligand and metal ions that appears slightly more pronounced for lithium and beryllium metal complexes. The metal ion affinity (MIA) and basis set superposition error (BSSE) corrected interaction energy were also computed for all the complexes. The effect of metal cations on the infrared (IR) stretching vibrational modes of amino N? H bond, side chain thiol group S? H bond, hydroxyl O? H bond, and Carbonyl C?O bond in cysteine molecules have also been studied. The nature of the metal ion‐ligand bond and the coordination properties were examined using natural bond order (NBO) at bond critical point (electron density and their Laplacian of electron density) through Atoms in Molecules (AIM) analyses. Copyright © 2010 John Wiley & Sons, Ltd.     

MC6Li6 (M = Li,Na and K): a new series of aromatic superalkalis

Organic superalkalis are carbon-based species possessing lower ionisation energy than alkali atom. We study the MC₆Li₆ (M?=?Li, Na, and K) complexes and their cations by decorating hexalithiobenzene with an alkali atom using density functional theory. All MC₆Li₆ complexes are stable against dissociation into M?+?C₆Li₆ fragments, irrespective of their charge. Furthermore, their degree of aromaticity increases monotonically from M?=?Li to K, unlike MC₆Li₆ ⁺ cations, which are not aromatic as suggested by their NICS values. The adiabatic ionisation energies of MC₆Li₆ (2.60–2.78?eV) and vertical electron affinities of MC₆Li₆ ⁺ (2.32–2.62?eV) suggest that MC₆Li₆ species form a new series of aromatic superalkalis. The superalkali nature of MC₆Li₆ ⁺ and its relation with NICS values are explained on the basis of the positive charge delocalisation. We believe that these species will not only enrich the aromatic superalkalis but also their possible applications will be explored.     

质谱和拉曼光谱对[M(H2O)n]+(M=Li,K)水合团簇的研究

采用质谱、拉曼光谱及理论计算对[M(H₂O)_n]+(M=Li,K)水合团簇进行了研究。质谱分析[M(H₂O)_n]+(M=Li,K)水合团簇的离子峰,推测其水溶液中最大水化数为12和13。采用拉曼光谱对浓度梯度相同的LiCl和KCl水溶液进行了讨论与比较,Li+和K+的水化作用导致~3 208 cm-1水结构拉曼峰发生了明显的变化,其中LiCl和KCl溶液的浓度分别在0~2.0和0~2.5 mol·L-1范围内,水化作用呈线性增强,浓度大于2.0和2.5 mol·L-1时,偏离线性关系,出现缔合。理论计算[M(H₂O)_n]+水合团簇结构和理论拉曼光谱表明,Li+,K+分别在n>4和n>6开始第二水化层,O-H伸缩振动频率发生了蓝移,氢键结构遭到了破坏,与实验结果一致。     

M-Uracil复合物(M=Ca2+和Mg2＋)特征振动的密度泛函理论分析

采用密度函数理论的B3LYP交换关联能泛函在6-311 G(2df,2p)基组水平上,对Ca2 、Mg2 与尿嘧啶(简称U)三种各互变异构体(简称U1、U2和U3)形成的复合物进行了优化计算,获得稳定复合物的构形,并对这些稳定复合物进行振动频率计算.分析计算结果发现由于离子的参与,单体分子振动的力常数和折合质量均会发生变化,导致红外振动谱线发生不同程度移动;进一步分析发现C-H和O-H键的氢原子作弯曲振动和伸缩振动的谱线移动不确定,直接与离子作用的氧原子参与的振动谱线会发生红移,不直接与离子作用的氧原子参与的振动谱线会发生蓝移.     

Calculation of anharmonic effects in the unimolecular dissociation of M2+(H2O)2 (M = Be,Mg, and Ca)

The anharmonic and harmonic rate constants of the unimolecular dissociation of M²⁺(H₂O)₂ (M = Be, Mg, and Ca) were calculated using the Rice–Ramsperger–Kassel–Marcus theory. The anharmonic effects of the reactions were investigated. The results show that the energy barrier of the dissociation of Be²⁺(H₂O)₂ is 68.47 kcal/mol, and the anharmonic (T_4000K = 4.28×10⁸ s^?1) and harmonic (T_4000K = 4.22×10⁸ s^?1) rate constants were close in value in both the canonical and microcanonical systems. The energy barriers of the two steps for the dissociation, Mg²⁺(H₂O)₂ → MgOH⁺+H₃O⁺, were 37.41 and 11.39 kcal/mol, and those for the dissociation, Ca²⁺(H₂O)₂ → CaOH⁺+H₃O⁺, were 21.15 and 26.42 kcal/mol. The anharmonic effect of the two reactions is significant and cannot be neglected in both the canonical and microcanonical systems. The comparison also shows that the rate constants of the dissociation of Ca²⁺(H₂O)₂ have the maximum values, while those of Be²⁺(H₂O)₂ have the minimum values in the three reactions; however, the anharmonic effect also shows the similar trend in the comparison.     

Vibrational and reorientational dynamics,crystal structure and solid–solid phase transition studies in [Ca(H2O)6]Cl2 supported by theoretical (DFT) calculations

[Ca(H₂O)₆]Cl₂ between 93 and 300 K possesses two solid phases. One phase transition (PT) of the first‐order type at = 218.0 K (on heating) and = 208.0 K (on cooling) was determined by differential scanning calorimetry. Thermal hysteresis of this PT (10 K), as well as the heat flow anomaly sharpness, suggests that the detected PT is a first‐order one. The entropy change value [ΔS ≈ 8.5 J mol⁻¹ K⁻¹ ≈ Rln(2.8)] associated with the observed PT suggests a moderate degree of molecular dynamical disorder of the high‐temperature phase. The temperature dependencies of the full width at half maximum values of the infrared band are due to ρ(H₂O)A₂ mode (at 205 cm⁻¹), and two Raman bands are arising from τ(H₂O)E and τ(H₂O)A₁ modes (at ca. 410 and 682 cm⁻¹, respectively), suggesting that the observed PT is associated with a sudden change of speed of the H₂O reorientational motions. The estimated mean value of activation energy for the reorientation of the H₂O ligands in the high‐temperature phase is ca. 11.4 kJ mol⁻¹ from Raman spectroscopy and 11.9 kJ mol⁻¹ from infrared spectroscopy. X‐ray single‐crystal diffraction measurement and spectroscopic studies (infrared, Raman and inelastic neutron scattering) also confirm that [Ca(H₂O)₆]Cl₂ includes two sets of differently bonded H₂O molecules. Ab initio calculations of the complete unit cell of one molecule of calcium chloride with a different number of water molecules (2, 4 and 6) have also been carried out. A comparison of Fourier Transform Infrared (FT‐IR), Fourier Transform Raman Scattering (FT‐RS) and inelastic neutron scattering spectroscopies results with periodic density functional theory calculations was used to provide a complete assignment of the vibrational spectra of [Ca(H₂O)₆]Cl₂. Copyright © 2016 John Wiley & Sons, Ltd.     

Nonlinear optical and structural properties of M@C N endohedrals (M = Li,Ca and Sc,N = 60 and 70)

We have investigated the static (ω = 0) and frequency-dependent nonlinear optical (NLO) properties of the M@C _N endohedrals (M = Li, Ca, Sc, N = 60 and 70) using the SSH (Su–Schrieffer–Heeger) approximation and sum-over-state (SOS) approach. Also, we study the effects of displacement and alkali, alkaline earth and lanthanide metal atoms and type of cage on the hyperpolarisabilities of the M@C _N endohedrals. The hyperpolarisability magnitudes and spectra are in agreement with experiment and the work of others using the SSH approximation. Our results indicate that the cage-type effect on the NLO spectra of M@C _N endohedrals is dramatic. Also, atom type has little effect on the highest peak value. These relationships between the atom and cage type and hyperpolarisability values may be beneficial to experimentalists when designing new NLO materials with large NLO responses.     

Density functional investigation of metal encapsulated X@C12Si8 heterofullerene (X=Li, Na, K, Be, Mg, Ca, Al, Ga)

The stability and the possible application of our recently reported SiC heterofullerenes inspire the investigation of their further stabilization through ion encapsulation. The endohedral complexes X@C₁₂Si₈, where X=Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Al³⁺, and Ga³⁺, are probed at the MPWB1K/6-311G? and B3LYP/6-311G* levels of theory. The optimized geometries show the expanding or contracting capability of C₁₂Si₈ in order to accommodate metal ion guests. The inclusion energies indicate the stability of the complexes compared to the components. Meanwhile, the calculated binding energies show the stabilization of C₁₂Si₈ through the inclusion of Be²⁺, Mg²⁺, Al³⁺, and Ga³⁺. The host-guest interaction that is probed through NBO atomic charges supports the obtained results. This study refers to “metal ion encapsulation” as a strategy for stabilization of SiC heterofullerenes.     

水合金属团簇M~+(H_2O)_n(M=Cu,Ag,Au;n=1-4)的结构和稳定性研究

利用密度泛函理论B3LYP方法优化了M~+(H_2O)_n(M=Cu,Ag,Au;n=1-4)团簇的几何结构,并对它们的稳定性和电子性质进行了系统研究.计算结果表明,Cu~+(H_2O)_n和Ag~+(H_2O)_n团簇的水合骨架结构由三个氧原子与金属离子相连接而成,而Au~+(H_2O)_n团簇则由两个氧原子与金属离子形成的线性结构而得到.通过计算的结合能和HOMO-LUMO能隙也发现:三种水合金属离子体系的稳定性大小为:Eb(Cu)=Eb(Au)Eb(Ag),但是Ag~+(H_2O)_n团簇具有较高的动力学稳定性.这些研究对于今后过渡金属离子水溶液性质的研究和应用提供了重要的理论参考.