Al_nMg_m(n+m=6,7;m=1,2)团簇的稳定性与电子结构

用遗传算法结合经验势对AlnMgm(n+m=6,7;m=1,2)的低能结构进行全局搜索,用从头计算方法研究了其稳定性和电子结构.计算表明AlnMgm存在多个能量相近的异构体,在Al Mg团簇中Mg-Mg相互作用远弱于Al-Al作用,稳定结构中Mg原子倾向于形成更多的Mg-Al键.自然键轨道(NBO)电荷分析表明Mg向Al转移电子,Al原子上的电荷大小强烈依赖于相连的Mg原子个数.电子结构分析表明随着原子数目的增大,占据轨道能级略有降低,同尺寸下掺杂一个Mg时能级更低;Al Mg团簇的能隙约为5.30 e V.     

AlmNin (m+n=2–4)二元合金团簇结构和稳定性的密度泛函研究

在密度泛函理论的B3PW91水平上, 优化计算了AlmNin (m+n=2–4)团簇的几何结构、团簇基态的结合能、最高占据轨道与最低空轨道之间的能级间隙和可能的分离能. 结果表明, 随着团簇尺寸的增加, 能级间隙呈现奇偶振荡规律; Al2Ni2团簇具有最高的结合能, 易分离成Ni原子和Al2Ni团簇; 含Al的合金团簇最易先分离出一个Al原子, 而含Ni的合金团簇没有这种趋势.     

AlB+n(n=2～10)团簇结构和红外振动光谱研究

用密度泛函理论的B3LYP方法在6-311G(d)水平上对AlB+n(n=2～10)团簇几何结构、稳定性、电子结构和成键特性进行了系统理论研究,得到了AlB+n(n=2～10)团簇的最稳定结构.结果表明,硼原子间容易聚集,铝原子处于整个硼原子集团的外围.与相应中性AlBn团簇相比,Al-B键作用变弱,使正价团簇(n=6...     

Al_mNi_n(m+n=2-4)二元合金团簇结构和稳定性的密度泛函研究

在密度泛函理论的B3PW91水平上,优化计算了Al_mNi_n(m+n=2-4)团簇的几何结构、团簇基态的结合能、最高占据轨道与最低空轨道之间的能级间隙和可能的分离能.结果表明,随着团簇尺寸的增加,能级间隙呈现奇偶振荡规律;Al_2Ni_2团簇具有最高的结合能,易分离成Ni原子和Al_2Ni团簇;含Al的合金团簇最易先分离出一个Al原子,而含Ni的合金团簇没有这种趋势.     

AlB+n(n=2~10) 团簇结构和红外振动光谱研究

用密度泛函理论的B3LYP方法在6-311G(d)水平上对AlB+n（n=2~10）团簇几何结构、稳定性、电子结构和成键特性进行了系统理论研究,得到了AlB+n（n=2~10）团簇的最稳定结构.结果表明,硼原子间容易聚集,铝原子处于整个硼原子集团的外围.与相应中性AlBn团簇相比,Al-B键作用变弱,使正价团簇（n=6和10除外）结构变化较大|对AlB+n（n=2~10）和相应中性团簇能隙的计算分析表明,AlB+n 团簇的稳定性有所增强,其中AlB+3、AlB+5和AlB+8团簇尤为显著|通过对最稳定构型红外振动光谱的研究分析表明,硼原子间对称或非对称振动、铝原子不动的振动模式更容易出现较强谱峰,即硼原子间更容易成键.     

Al_2S_n~±(n=2—10)团簇结构特征和稳定性的密度泛函理论研究

采用密度泛函理论的B3LYP方法,在6-311G**水平上对Al2S±n(n=2—10)团簇的几何结构和电子结构进行了理论计算.讨论了铝硫二元离子混合团簇基态结构的变化规律、电荷转移和成键特征.结果表明,在S簇中掺杂Al原子会使Sn结构发生明显改变.Al2S±n团簇基态结构是以Al2S2四元环为骨架或桥梁,分别与S原子或S簇相结合形成单环到三环的平面和立体结构.结构中化学键键型和成键数目影响团簇的稳定性.通过对基态结构的解离能和能量二次差分值的分析得到了Al2S±n团簇的稳定性信息.     

Co_mAl_n(m+n≤6)团簇的结构和磁性理论研究

采用密度泛函理论中的广义梯度近似(DFT-GGA)对ComAln(m+n 6)合金团簇进行了系统的几何、电子结构和磁性质研究.研究结果发现ComAln(m+n 6)团簇最稳定结构倾向于形成Co—Al成键数最多的构型,其中的Co—Al二元合金团簇的最稳定结构类似于纯钴团簇.随着Al原子数的增多,团簇的平均磁矩呈线性降低趋势.ComAl(m=2—5)团簇的总磁矩均比Com+1团簇的小4μB,与实验上对较大CoNAlM团簇的磁性检测结果获得了很好地符合.ComAln团簇磁性的降低主要归因于非磁性Al元素的掺入以及Al掺杂后Co原子的整体自旋极化减弱.     

MB80/-(M=Li、Na、Rb、Cs)团簇的几何结构和电子特性的研究

本文结合CALYPSO软件和密度泛函理论，详细研究了MB₈^0/-(M=Li、Na、Rb、Cs)团簇的几何结构和成键特性.结构分析结果表明，MB₈^0/-团簇的基态结构都具有相似的几何构型，均为七棱锥状结构，并且随着掺杂原子的原子序数的增加，其M-B键的键长呈增加的趋势.通过稳定性分析，我们发现Li B₈^-团簇的最高占据分子轨道与最低未占据分子轨道之间的能隙(HOMO-LOMO能隙)以及结合能(E_b)最大，因此这个团簇是体系中相对稳定的结构.电荷转移分析表明，掺杂的碱金属原子在所研究体系中充当着电子供体的角色.最后，成键分析的结果显示，Li B₈^-团簇的稳定性来源于B原子的2p轨道以及Li原子的2s和2p轨道在HOMO和LUMO的高贡献;适应性自然密度划分分析显示，B和Li原子都参与了成键，这同样有利于Li B₈^-1团簇的高稳定性的形成.希望我们的工作...     

H2在Al12X (X=Al, Ni, Cu)团簇表面解离吸附的第一性原理研究

以Ni和Cu原子中心替换的二十面体Al12X(X=Ni、Cu)团簇为基体、采用密度泛函理论系统计算研究了H原子及H2分子在团簇表面的吸附,并对比了纯Al13团簇对H及H2的吸附,结果表明：相对于纯Al13中H原子的桥位吸附、掺杂团簇Al12X(X=Ni、Cu)中H原子均吸附于团簇顶位;无论是吸附H原子还是H2分子,Al12Ni的几何结构均发生大的畸变;相较H2在纯Al13团簇表面的解离吸附,H2在掺杂团簇Al12X(X=Ni、Cu)表面的解离反应过程中反应能均增大、势垒均降低,这表明掺杂团簇Al12X(X=Ni、Cu)相较纯Al13团簇更有利于H2解离吸附的发生。     

H_2在Li掺杂Al_7C~+上吸附的理论研究

利用密度泛函理论研究了H2分子在Li掺杂Al7C+团簇上的吸附.对于Al7C+团簇,H2分子的吸附能仅为-0.017eV,掺杂Li原子到Al7C+团簇可以明显增强对H2分子的吸附.吸附一个H2分子时吸附能可以达到-0.151eV,吸附四个H2分子的平均吸附能为-0.073eV.根据自然键轨道分析,电荷从Li原子向Al7C+团簇转移,带正电的Li离子极化H2分子并且增强了H2分子与Al7CLi+团簇之间的相互作用.     

Ratio m(c)/m(s) with Wilson fermions

We determine the quark mass ratio m(c)/m(s) on the lattice, using Wilson-type fermions. Configurations with N(f)=2 dynamical clover-improved fermions by the QCDSF Collaboration are used, which were made available through the ILDG. In the valence sector we use a sophisticated, mass-independently O(a)-improved Wilson-type action with small cutoff effects even in the charm mass region. After an extrapolation to the physical pion mass, to zero lattice spacing and to infinite box volume, we find m(c)/m(s)=11.27(30)(26).     

Nanodopant-induced band modulation in AgPb(m)SbTe(2+m)-type thermoelectrics

The structure-property relation is a key outstanding problem in the study of nanocomposite materials. Here we elucidate the fundamental physics of nanodopants in thermoelectric nanocomposites XPb(m)YTe(2+m) (X = Ag, Na; Y = Sb, Bi). First-principles calculations unveil a sizable band-gap widening driven by nanodopant-induced lattice strain and a band split-off mainly caused by the spin-orbit interaction in nanodopant. Boltzmann transport calculations on PbTe with modified band mimicking nanodopant-induced modulations show significant but competing effects on high-temperature electron transport behavior. These results offer insights for understanding experimental findings and optimizing thermoelectric properties of narrow band-gap semiconductor nanocomposites.     

Conservation Laws of K(m, n) and mK(m, n) Equations

Based on the rank analysis method, algorithmization idea, and symbolic computation, in this paper we have presented a method to construct the conservation laws for nonlinear evolution equations. The polynomial conservation laws for K (n 2, n) equations and mnK(m, n) equations are found by using of this approach and some new results have been obtained.     

Conservation Laws of K（m,n） and mK（m,n） Equations

Based on the rank analysis method, algorithmization idea, and symbolic computation, in this paper we have presented a method to construct the conservation laws for nonlinear evolution equations. The polynomial conservation laws for K (n 2,n) equations and mK (m,n) equations are found by using of this approach and some new results have been obtained.     

New value of m(mu)/m(e) from muonium hyperfine splitting

The complete contribution to the muonium hyperfine splitting of relative order alpha(3)(m(e)/m(mu))lnalpha is calculated. The result is much smaller than suggested by a previous estimate and leads to a 2sigma upward shift of the most precise value for the muon-electron mass ratio. Analogous contributions are calculated for the positronium hyperfine splitting, where a discrepancy with experiment remains.     

Irreducible Representations of the Quantum Group Uq(m + n) in Uq(m)⊕ Uq(n) Basis

Irreducible represen tations of U_q(m + n) in U_q(m) ⊕ U_q(n) basis are discussed. The noncanonical basis of U_q(m + n) are expanded in terms of its canonical basis. The expansion coefficients or subduction coefficients of U_q (m + n)↓ U_q(m) ⊕ U_q(n) are derived from the subduction coefficients of Hecke algebras.     

Enhanced Sensitivity to Variation of m(e)/m(p) in molecular spectra

We propose new experiments with high sensitivity to a possible variation of the electron-to-proton mass ratio mu identical with m(e)/m(p). We consider a nearly degenerate pair of molecular vibrational levels, each associated with a different electronic potential. With respect to a change in mu, the change in the splitting between such levels can be large both on an absolute scale and relative to the splitting. We demonstrate the existence of such pairs of states in Cs2, where the narrow spectral lines achievable with ultracold molecules make the system promising for future searches for small variations in mu.     

q-Oscillator realizations of the quantum superalgebrassl q (m,n) andosp q (m, 2n)

Realizations of the quantum superalgebras corresponding to theA(m, n), B(m, n), C(n+1), andD(m, n) series are given in terms of the creation and annihilation operators ofq-deformed Bose and Fermi oscillators.