Atoms-in-molecules treatment of Li 2 + and Li2 using optimum Gaussian approximations of Li+ and Li eigenstates

Expectation energies for the Li⁺, Li and Li^– ground states and for the 1s ²2p Li excited state are individually minimized with respect to variation of parameters in Gaussian lobe expansions of the 1s, 2s and 2p AO's. A new technique is used to control 1s–2s orthonormality. The resulting approximate many-electron atomic eigen-functions are utilized for determining interatomic matrix elements in atoms-in-molecules (AIM) calculations on the two lowest energy ¹ _g ⁺ states of Li₂ and on the lowest energy ² _g ⁺ and ² _u ⁺ states of Li ₂ ⁺ . For R greater than 4 a.u., convergence to exact theoretical AIM limits, within about 0.001 h.u., is obtained by using three-term expansions. Three-structure Li₂ and two-structure Li ₂ ⁺ AIM energies are above experimental by 0.005 and 0.007 h.u., respectively. It is conjectured that an AIM model extended to permit scaling of valence electrons independently of innershell electrons would reduce significantly these energy differences.

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Zusammenfassung Die Energieerwartungswerte für die Grundzustände von Li⁺, Li und Li^–1 sowie für den angeregten Zustand 1s² 2p von Li werden einzeln bezüglich der Variationsparameter einer Entwicklung der 1s-, 2s- und 2p-Atomorbitale nach Gaußfunktionen minimisiert. Zur Kontrolle der Orthonormalität der 1s- und der 2s-Funktion wird eine neue Technik angewandt. Die resultierenden angenäherten Atomeigenfunktionen werden bei Atom-in-Molekül (AIM)-Rechnungen für die zwei niedrigsten ¹ _g ⁺ -Zustände von Li₂ und die niedrigsten Zustände der Symmetrie ² _g ⁺ und ² _u ⁺ von Li ₂ ⁺ verwendet. Für einen Atomabstand R größer als 4 A.E. wird mit einer Entwicklung mit drei Termen eine Annäherung bis zu 0,001 A.E. an den exakten theoretischen AIM-Grenzwert erreicht. Die AIM-Energiewerte, die mit drei Resonanzstrukturen von Li₂ bzw. zwei Resonanzstrukturen von Li ₂ ⁺ erhalten werden, liegen 0,005 A.E. bzw. 0,007 A.E. über den experimentellen Werten. Es wird angenommen, daß eine Erweiterung des AIM-Modells, bei der eine Skalierung der Valenzelektronenfunktionen unabhängig von den inneren Elektronen möglich ist, diese Energiedifferenz stark herabsetzen würde.

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Résumé Les énergies de l'état fondamental de Li⁺, Li et Li^–, et de l'état excité 1s²2p de Li sont individuellement minimisées par rapport à la variation des paramètres dans le développement gaussien des orbitales atomiques 1s, 2s et 2p. Une technique nouvelle est utilisée pour contrler l'orthonormalité 1s–2s. Les fonctions d'onde polyélectroniques approchées résultantes sont utilisées pour des calculs du type atomes dans les molécules (ADM) pour les deux états ¹ _g ⁺ de plus basse énergie de Li₂ et sur les états ² _g ⁺ et ² _g ⁺ de plus basse énergie de Li₂. Pour R supérieur à 4 u.a., la convergence vers les limites théoriques exactes ADM est obtenue avec un développement à trois termes, à 0,001 u.a. près. Les énergies ADM à trois structures pour Li2 et á deux structures pour Li2 sont respectivement á 0,005 et 0,007 a.u. au dessus des énergies expérimentales. On émet l'hypothése qu'un modéle ADM étendu pour permettre le calibrage des électrons de valence indépendamment des électrons des couches internes réduirait d'une manière significative ces différences d'énergie.

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Supported in part by National Science Foundation Grant GP 25415     

锂金属电池研究中对称电池的短路现象

锂金属是具有高能量密度的负极材料,是下一代高能量密度电池研究的重点。在锂金属负极的改性研究中,锂对称电池是最常用的测试对象,但判断其短路的依据尚未统一,因此存在部分对短路数据的解析错误。本文利用原位电池对锂沉积过程中由于枝晶生长导致的短路现象进行了描述,对锂金属对称电池在充放电过程中的短路现象进行了分类和讨论。通过区分硬短路、软短路及电池活化过程,提出了判断锂对称电池中枝晶生长及电池短路的依据,为判定锂金属负极改性方法的有效性提供参考。     

Calculated ro-vibrational spectrum of 7Li+3 and 7Li2 6Li+

Calculated ro-vibrational energy levels (J ⩽ 4) and transition intensities are presented for the two most abundant isotopomers of Li⁺₃. The calculations use the recent ab initio potential energy surface of Searles et al. (Spectrochim. Acta 43A, 699 (1987); 44A, 505 (1988); 44A, 985 (1988)). The rotational levels of the ground state and vibrational fundamentals are given in terms of parameterised Hamiltonians due to Watson retaining terms to fourth-order. The small splitting of the degenerate ν₂ mode in the mixed isotopomer leads to strong Coriolis coupling between the ν₂ and ν₃ in ⁷Li₂ ⁶Li⁺.     

Zur Kenntnis der Chlorid-Spinelle Li2MgCl4, Li2MnCl4, Li2FeCl4, Li2CdCl4

About the Chloride Spinels Li₂MgCl₄, Li₂MnCl₄, Li₂FeCl₄, Li₂CdCl₄ FIR, Raman, and X-ray data of the spinel type chlorides Li₂TCl₄ (T = Mg, Mn, Fe, Cd) are presented. The vibrational spectra indicate that there is no 1:1 ordering on the octahedral sites of the lattice. Both DTA measurements and high temperature X-ray photographs show that the chloride spinels undergo a reversible phase transition to a cubic high temperature defect structure at 535°C (Li₂MgCl₄), 460°C (Li₂MnCl₄) and 385°C (Li₂CdCl₄), which has unit cell dimensions two times smaller than the spinel lattice. Disordering of the lithium sublattice still begins at much lower temperatures, as measurements of the electric conductivity indicate.     

Lithium-ion Mobility in Li6B18(Li3N) and Li Vacancy Tuning in the Solid Solution Li6B18(Li3N)1−x(Li2O)x

All-solid-state batteries are promising candidates for safe energy-storage systems due to non-flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open-framework boron structure. The host–guest structure Li₆B₁₈(Li₃N) comprises large hexagonal pores filled with Li₇N] strands that represent a perfect cutout from the structure of α-Li₃N. Variable-temperature ⁷Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol⁻¹ and thus much lower than pristine Li₃N. The formation of the solid solution of Li₆B₁₈(Li₃N) and Li₆B₁₈(Li₂O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li₃N and Li₂O.     

Interactions and dynamics in Li+Li2 ultracold collisions

A potential energy surface for the lowest quartet electronic state ((4)A(')) of lithium trimer is developed and used to study spin-polarized Li+Li(2) collisions at ultralow kinetic energies. The potential energy surface allows barrierless atom exchange reactions. Elastic and inelastic cross sections are calculated for collisions involving a variety of rovibrational states of Li(2). Inelastic collisions are responsible for trap loss in molecule production experiments. Isotope effects and the sensitivity of the results to details of the potential energy surface are investigated. It is found that for vibrationally excited states, the cross sections are only quite weakly dependent on details of the potential energy surface.     

锂金属负极的可逆性与沉积形貌的关联

高能量密度二次电池的商业化将会推动便携式电子设备和电动车的飞速发展。锂金属电池因具有较高的理论能量密度而受到研究者的广泛关注。然而,锂金属负极较低的库仑效率(CE)和枝晶生长等问题,严重制约了锂金属电池的发展。库仑效率是衡量电池体系可逆性的关键参数之一,锂金属负极的库仑效率在不同电解液中存在较大的差异,本文以四种常见的电解液为例,包括1 mol·L^-1六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯电解液,1 mol·L^-1六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯+5%(w)氟代碳酸乙烯酯电解液,1 mol·L^-1双(三氟甲烷磺酰)亚胺锂-乙二醇二甲醚/1,3二氧戊环+2%(w)硝酸锂电解液,以及4 mol·L^-1双氟磺酰亚胺锂-乙二醇二甲醚电解液,利用原子力显微镜研究了不同电解液体系中锂金属的生长行为,探讨了锂金属沉积形貌与其库仑效率之间的联系,为发展高效的锂金属负极提供了参考依据。     

The impedance of the Li+/Li electrode in SOCl2

Impedance measurements have been made on a lithium electrode in SOCl₂ containing 1.8 M LiAlCl₄. Impedance loci were recorded over a range of frequencies at a series of potentials.The results confirm the existence of a film on the Li electrode which grows continuously with time. Kinetic data for the Li⁺/Li ion exchange were estimated by arranging for measurements to be made as rapidly as possible and after a practical minimum time of electrode/electrolyte contact. The exchage current density for the lithium electrode was estimated under our best conditions to be 0.48 mA/cm² and α for the Li⁺ couple ≈ 0.59.     

Li metal-free rechargeable all-solid-state Li2S/Si battery based on Li7P3S11 electrolyte

Journal of Solid State Electrochemistry - As high energy density and enhanced safety are required for the lithium-ion battery development, all-solid-state battery has attracted significant...     

Electric Properties of Solid Solutions in the Systems Li6MoN4−Li7NbN4 and Li6WN4−Li7TaN4

The phase balance and electric properties of products in the systems Li₆MoN₄–Li₇NbN₄ and Li₆WN₄–Li₇TaN₄ are studied. It is shown that continuous series of solid solutions whose lithium-cation conductance decreases during mutual doping exist in either system. The activation energies for the long- and short-range motion of lithium charge carriers, determined from the electroconductance and ⁷Li NMR data, equal 55 and 46 or 25 and 14 kJ mol^–1 for the initial compounds of the first and second systems, respectively. The difference that large is attributed to a large contribution of the coulombic correlation for the hops of lithium charge carriers in both systems. Basic parameters of the correlation (time, distance, relaxation time) are calculated from experimental data. The strong correlation in the systems is presumed to stem from a weak screening of the coulombic field in the nitrides, rather than from a high concentration of charge carriers.     

High accuracy ab initio studies of Li6+, Li6-, and three isomers of Li6

The structures and energetics of Li(6) (+), Li(6) (-) and three isomers of Li(6) are investigated using the coupled-cluster singles, doubles and perturbative triples [CCSD(T)] method with valence and core-valence correlation consistent basis sets of double- to quadruple-zeta quality (cc-pVXZ and cc-pCVXZ, where X=D-Q). These results are compared with qualitatively different predictions by less reliable methods. Our results conclusively show that the D(4h) isomer is the global minimum structure for Li(6). It is energetically favored over the C(5v) and D(3h) structures by about 5.1 and 7.1 kcal mol(-1), respectively, after the inclusion of the zero-point vibrational energy (ZPVE) correction. Our most accurate total atomization energies are 123.2, 117.6, and 115.7 kcal mol(-1) for the D(4h), C(5v), and D(3h) isomers, respectively. Comparison of experimental optical absorption spectra with our computed electronic spectra also indicate that the D(4h) isomer is indeed the most stable structure. The cation, anion, and some higher spin states are investigated using the less expensive cc-pCVDZ basis set. Adiabatic ionization energies and electron affinities are reported and compared with experimental values. Predictions of molecular properties are found to be sensitive to the basis set used and to the treatment of electron correlation.     

Theory of laser enhancement of ultracold reactions: the fermion-boson population transfer by adiabatic passage of 6Li+6Li7Li(Tr=1 mK)-->6Li6Li+7Li(Tp=1 mK)

We present a new theory of population transfer by adiabatic passage. This theory relates laser catalysis to adiabatic passage, enhancing chemical reactions with the freedom to choose the translational energies of the reactants and products separately. The process, A+BC<-->(Planck's over omega(p) )ABC*(v)<-->(Planck's over omega(s))AB+C, involves two laser fields that are slowly varying so the process is adiabatic, and sufficiently intense so the population of the intermediate bound complex (ABC) is minimized. We apply this theory to the collinear exchange reaction (6)Li+(7)Li(2)(T(r))<-->(Planck's over omega(p))((6)Li(7)Li(7)Li)*<-->(variant Planck's over 2piomega(s) ) (6)Li(7)Li(T(p))+(7)Li. We show that at translational energies T(p)=T(r)=1 mK with a narrow energy bandwidth of delta(E)=0.01 mK, we can obtain nearly total (> or =98%) population transfer from the reactant to the product states. This can be done with a pump laser and a Stokes laser in an "intuitive" sequence (t(p)相似文献