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用Hueckel-Hubbard理论及作者所建议的参数化方法,对碱金属团簇An,A^+n,A^-n的结构和碎化进行计算和分析,结果表明:n≤5时团簇呈平面结构,几率大的碎化对应着中性单原子或中性二聚物的生成,团簇的稳定性随n的变化呈出奇偶性,中性簇与离子簇的奇偶性上反,这些定性结果与实验及其它更精确算法的结果基本一致。 相似文献
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C40异构体的结构和稳定性的理论研究 总被引:1,自引:0,他引:1
利用Gaussian98程序,采用密度泛函(DFT)方法中的B3LYP,选用6-31G基组对富勒烯(Fullerene)C40的6种异构体[D5d,Td,D2h,C3v,D2(Ⅰ),D2(Ⅱ)]进行了几何构型优化,其中,对于Td对称性的C40由于易发生Jahn-Teller畸变,则降低其对称性为D2d,再进行优化.对它们的平衡几何和电子结构进行了比较具体的分析,同时,根据计算得到的总能量推断出这6种异构体的稳定性顺序是D2(Ⅰ)>D5d>Td>C3v>D2h>D2(Ⅱ). 相似文献
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Layer-structured crystals of β-MNCl (M=Zr,Hf) could be electron-doped by reactions with different alkali metal azides RN3 (R=Li,Na,K,Rb), and controlling the amounts with the molar ratios of azides to β-MNCl. All the prepared compounds show superconductivity with the same transition temperatures at 13.5 K for β-ZrNCl and 23.5 K for β-HfNCl. However the different alkali metal azides RN3 show different reactivity with β-MNCl, and the properties of the products such as superconducting fractions, the lattice constant, and stability against thermal or air, are very dependent on the kinds of alkali metals used. Based on the the results of SQUID measurements, it can be concluded that NaN3 and KN3 are the best react agents for β-ZrNCl and β-HfNCl respectively. 相似文献
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The structural stabilities and electronic structures of Ga atomic chains are studied by the first-principles plane wave pseudopotential method based on the density functional theory. The present calculations show that gallium can form planar chains in linear-, zigzag- and ladder-form one-dimensional structures. The most stable one among the studied structures is the zigzag chain with a unit cell rather close to equilateral triangles with four nearest neighbors, and all the other structures are metastable. The relative structural stability, the energy bands and the charge densities are discussed based on the ab initio calculations and the Jahn-Teller effect. 相似文献
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采用DFT,QCISD和CCSD(T)等理论计算方法对三重态SiCP2异构体的结构和稳定性进行了理论研究.在B3LYP/6-311G(d)水平下,共计算得到由17个过渡态相连接的15个异构体.在CCSD(T)/6-311 +G(2df)//QCISD/6-311G(d)水平下,考虑重点振动能相对能量最低的三元环状异构体P-cCSiP 8(0.0 kJ/mol)及四元环状结构的cPCSiP 4具有相当大的动力学稳定性,在一定的实验室和星际条件下可能被检测到.另外,对它们的成键性质也进行了分析. 相似文献
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B3LYP/6-31G* density functional theory calculations have been carried out on the structure and stability of ten B20N20 clusters. It was found that two new proposed isomers with two octagons, twelve hexagons, eight squares in Cab and C2 symmetry were more stable than the isomer with sixteen hexagons and six squares in C2 symmetry which was previously deemed to the most stable by 79.5 and 13.8 kJ/mol respectively. The isomer with two decagons in S10 symmetry is much higher in energy than the most stable structure in C4h symmetry by 637.2 kJ/mol. 相似文献
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A. G. Anshits E. N. Voskresenskaya V. V. Rivanenkov V. A. Nasluzov K. M. Neiman 《Reaction Kinetics and Catalysis Letters》1992,46(2):285-291
Quantum-chemical modeling of Li-doped MgO complexes had been carried out. Interaction of anion vacancies with O2 molecule has been considered. It has been confirmed that this interaction can lead to the pronounced activation of lattice oxygen as a reactant participating in the oxidative coupling of methane.
- MgO: O– , . . , , . .相似文献
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通过Sn助熔剂法在高温下合成一种Zintl相化合物α-BaZn2P2,通过X射线单晶衍射确定其晶体结构与α-BaCu2S2同构,属于Pnma空间群。α-BaZn2P2的晶格参数为:a=0.976 78(5)nm,b=0.413 34(2)nm,c=1.060 55(5)nm。与高温相β-BaZn2P2的层状结构不同,低温相α-BaZn2P2具有三维网格结构。其中ZnP4四面体通过共边和共顶2种方式连接形成阴离子框架,Ba2+作为阳离子填隙其中。基于密度泛函理论计算了该化合物的能带结构和态密度,结果表明该化合物是窄带隙半导体(Eg=0.4 eV)。另外,DSC和变温XRD结果表明高温下α-BaZn2P2分解为Ba4P5,ZnP4等二元相。 相似文献
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通过Sn助熔剂法在高温下合成一种Zintl相化合物α-BaZn2P2,通过X射线单晶衍射确定其晶体结构与α-BaCu2S2同构,属于Pnma空间群。α-BaZn2P2的晶格参数为:a=0.976 78(5) nm,b=0.413 34(2) nm,c=1.060 55(5) nm。与高温相β-BaZn2P2的层状结构不同,低温相α-BaZn2P2具有三维网格结构。其中ZnP4四面体通过共边和共顶2种方式连接形成阴离子框架,Ba2+作为阳离子填隙其中。基于密度泛函理论计算了该化合物的能带结构和态密度,结果表明该化合物是窄带隙半导体(Eg=0.4 eV)。另外,DSC和变温XRD结果表明高温下α-BaZn2P2分解为Ba4P5,ZnP4等二元相。 相似文献
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Au/H 相似性的研究是现代化学中的一个热门话题. 我们从理论上报道Au/H 相似的新成员: 共价化合物B2Au4, 离子化合物Al2Au4和BAlAu4. 采用密度泛函和波函数理论方法对比研究了缺电子体系B2Au4、Al2Au4和BAlAu4的几何和电子结构. 详细讨论了它们基态结构的轨道、适应性自然密度划分(AdNDP)和电子局域函数(ELF)分析. 计算结果表明稍微扭曲变形的C2B2Au4是基态结构, 在这个共价化合物中含有两个B―Au―B三中心二电子(3c-2e)键. 然而C3v Al+(AlAu4)-和C3v Al+(BAu4)-被研究证明是含有三个X―Au―Al 三中心二电子键的类盐化合物(在Al2Au4中X=Al, BAlAu4中X=B). Al2Au4和BAlAu4是至今为止首例报道的在离子缺电子体系中含有金桥键的化合物. 同时计算了B2Au4-、Al2Au4- 和BAlAu4- 阴离子基态结构的绝热剥离能和垂直剥离能, 为实验表征提供依据. 文中报道的金桥键为共价键和离子键相结合的缺电子体系提供了一个有趣的键合模式, 有助于设计含有高度分散金原子的新材料和催化剂. 相似文献
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使用密度泛函理论(DFT)-B3LYP/6-31G*方法研究了B、N、Si、P和Co在C50和C70中的掺杂能和电子结构, 并基于曲率理论和电子结构探讨了掺杂富勒烯的结构稳定性. 计算结果表明, 掺杂能随着原子曲率的增大而减小, 随着掺杂物种原子半径的增大而增大, B、N、P和Co的掺杂有利于C50结构的稳定, 而B和N的掺杂不利于C70结构的稳定; 除了用于反映原子活性的曲率主要决定掺杂反应性, 各不等价碳原子在C50和C70的最高占据分子轨道(HOMO)中所占成分对掺杂能的影响也很大, 且其成分越大越有利于掺杂. 此外, 掺杂原子得失电子情况与其电负性有关. 本工作将为富勒烯结构稳定性的研究提供理论依据. 相似文献
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采用基于密度泛函理论的第一性原理计算方法,计算了锂离子电池LiMnPO4正极材料的电子结构。计算结果表明:当Li+嵌入体系后,O和P的原子布居变化较小,电子向金属原子的转移明显得到加强。Li+和O2-有弱相互作用,当Li+离子脱出以后,氧原子所得到的电子数减小,导致布居减小。锂是以离子形式存在的于LiMnPO4正极材料中。在LiMnPO4和MnPO4体系中,Mn原子具有磁性,其磁矩分别为4.78μB和3.84μB,其余原子磁性近似为0。氧为负离子,带负电荷,而P和Mn则为正离子。O2p与P3s、P3p轨道发生有效重叠,并形成共价键,Mn3d和O2p之间能够有效地发生重叠并形成共价键。在放电过程中有电子从外电路进入正极,大部分电子所带电荷分布在Mn原子上。 相似文献
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Ni/SiO2 catalysts promoted by alkali metals K and Cs or alkaline earth metals Mg, Ca, Sr and Ba were prepared, characterized by H2-TPR and XRD, and used for the production of synthesis gas via methane reforming with CO2. Though K and Cs promoted Ni catalysts could eliminate coke deposition, the reforming activity of these promoted catalysts was decreased heavily. Mg and Ca promoted Ni/SiO2 catalysts exhibited excellent coke resistance ability with minor loss of the reforming activity of Ni/SiO2. Ba showed poor coke resistance ability and small amount of Sr increased the formation of coke. The possible mechanism of these promoters was discussed. 相似文献
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The generalized gradient approximation (GGA) based on density functional theory (DFT) was used to analyze the structural and electronic properties of Fe@C60 and C59Fe for comparison. Among the six possible optimized geometries of Fe@C60, the most favorable endohedral site of Fe atom is under the center of a hexagon ring, i.e., Fe@C60-6. The Energy gap (Eg) of Fe@C60-6 is smaller than those of C59Fe and C60, indicating the higher chemical reactivity. The magnetic moment of Fe atom in Fe@C60-6 is preserved to some extent though there is the hybridization between the ge atom and C atoms of the cage, in contrast to the completely quenched magnetic moment of the Fe atom in C59Fe. 相似文献
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锂离子电池镍掺杂尖晶石LiMn2O4正极材料的电子结构 总被引:2,自引:0,他引:2
采用密度泛甬平面波赝势方法对LiMn2O4和LiNi0.5Mn1.5O4的几何结构进行了优化,并计算了相应的电子结构.计算的结果表明:在Li 脱嵌前后,LiMn2O4和LiNi0.5Mn1.5O4均为导体,且锂元素主要以离子形式存在于两种材料中,O2p轨道与Mn(Ni)的3d轨道形成了较强的共价键.Li 嵌入导致Mn(Ni)3d轨道的态密度峰发生移动.Ni的掺杂导致Mn(Ni)和O2p轨道的成键作用得以加强,电子在Mn(Ni)3d轨道的填充发生变化,从而提高了电池的充放电电压. 相似文献
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使用GGA+U方法研究了CaO或BaO与Sm2O3共掺杂CeO2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时BaSmCe30O63体系最稳定;Sm靠近,Ca远离氧空位时CaSmCe30O63体系最稳定。BaSmCe30O63和CaSmCe30O63体系中均不存在Ce4+变价。对CaSmCe30O63体系氧离子迁移的研究发现,当氧离子迁移到空位时,迁移能大小顺序为Em(3→V)< Em(1→V)< Em(4→V)< Em(2→V),这一规律源于氧离子与低价掺杂离子产生负电势之间的排斥作用;对BaSmCe30O63体系氧离子迁移的研究发现,当空位迁移到周围氧离子时,迁移能大小顺序为Em(V→3)< Em(V→5)< Em(V→1),这一规律源于氧空位产生的正电势与低价掺杂离子产生的负电势之间的吸引作用。此外,CaSmCe30O63体系最小迁移能小于SmCe31O63体系,证实了CeO2-Sm2O3-CaO体系离子电导率大于CeO2-Sm2O3体系的实验结果。 相似文献
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Structures and thermodynamic properties of the imidoboranes (HBNH)n (n=1-16) have been investigated theoretically at the B3LYP/6-31G^* level of theory. Needle-shaped oligomers that violate the isolated square rule were found to be more stable than cage isomers. The needle-shaped oligomer with n=16 was predicted to be exceptionally stable at low temperature, hexamer and octamer clusters dominated the gas phase at higher temperature. The highest oligomerization degree of the spontaneous cluster fomation has been estimated. It was concluded that generation of the gas phase (HBNH)n clusters with oligomerization degree n ≥24 was viable, making these species possible intermediates involved in the gas phase generation of BN nanoparticles. 相似文献