Interphase Formation of PEO20:LiTFSI-Li6PS5Cl Composite Electrolytes with Lithium Metal.

Composite polymer electrolytes (CPEs), consisting of solid electrolyte particles embedded within a solid polymer electrolyte matrix, are promising materials for all-solid-state batteries because of their mechanical properties and scalable production processes. In this study, CPEs consisting of PEO20:LiTFSI blended with 1, 10, and 40 wt % (CPE40) of the Li6PS5Cl electrolyte filler are prepared by a slurry-based process. The incorporation of Li6PS5Cl improves the lithium-ion conductivity from 0.84 mS cm-1 (PEO20:LiTFSI) to 3.6 mS cm-1 (CPE40) at 80 °C. Surface-sensitive X-ray photoelectron spectroscopy (XPS) reveals LiF, polysulfides, and Li3PO4 on the CPE surface, originating from decomposition reactions between PEO20:LiTFSI and Li6PS5Cl. The decomposition products influence the formation of the solid electrolyte interphase (SEI) at the lithium metal | CPE interface, resulting in a reduced SEI resistance of 3.3 Ω cm2 (CPE40) compared to 5.8 Ω cm2 (PEO20:LiTFSI) at 80 °C. The SEI growth follows a parabolic rate law and the growth rate declines from 1.2 Ω cm2 h-0.5 (PEO20:LiTFSI) to 0.57 Ω cm2 h-0.5 (CPE40) during thermal aging at 80 °C. By substituting CPEs for PEO20:LiTFSI in lithium plating and stripping experiments, the increase in SEI resistance was reduced by more than 75%. In order to get a deeper understanding of the SEI formation process, in situ XPS measurements were carried out where the lithium metal is successively deposited on the CPE sample and XPS is measured after each deposition step. On the basis of these measurements, a multistep decomposition mechanism is postulated, including the formation of LiF and Li2S as key components of the SEI.

Properties of the Interphase Formed between Argyrodite-Type Li6PS5Cl and Polymer-Based PEO10:LiTFSI.

All-solid-state lithium metal batteries using thiophosphate solid electrolytes (SE) present a promising alternative to state-of-the-art lithium-ion batteries due to their potentially superior energy and power. However, reactions occurring at the lithium metal | SE interface result in an increasing internal resistance and limited cycle life. A stable solid polymer electrolyte (SPE) may be used as protective interlayer to prevent the SE from direct contact and reaction with lithium metal. This creates a new and rarely studied heteroionic interface between the inorganic SE and the SPE, which we investigate here. The interface resistance between argyrodite-type Li6PS5Cl and a poly(ethylene oxide)/LiTFSI-based SPE is quantified by four-point electrochemical impedance measurements using two wire-shaped reference electrodes (2.4 Ω cm2 at 80 °C). Two distinct processes are observed and attributed to lithium-ion conduction through a formed solid-polymer electrolyte interphase (SPEI) and an ionic charge-transfer (CT) process. The SPEI predominantly consists of polysulfides and lithium fluoride (LiF), as identified by X-ray photoelectron spectroscopy (XPS) analysis. A temperature-enhanced SPEI growth is observed using electrochemical impedance spectroscopy (EIS) and depth profiling combined with time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results highlight the importance of four-point measurements to determine electrolyte-electrolyte interface properties. Overall, the low resistance and low activation energy of the SPEI makes the SPE interlayer an attractive candidate to protect Li6PS5Cl from decomposition at the lithium metal anode.

Synthesis of Industrially Relevant Carbamates towards Isocyanates using Carbon Dioxide and Organotin(IV) Alkoxides.

A straightforward phosgene-free synthesis of aromatic isocyanates and diisocyanates is disclosed. Theoretical investigations suggested that the insertion of carbon dioxide (CO2 ) by dialkyltin(IV) dialkoxides could be used to convert aromatic amines into aromatic mono- and dicarbamates. Here we show, that methyl phenylcarbamate (MPC) from aniline using organotin(IV) dimethoxide and CO2 can be formed in high yield of up to 92 %, experimentally corroborating the predictions of density functional theory (DFT) calculations. MPC was then separated from the tin oxide residues and converted into phenyl isocyanate. Furthermore, organotin(IV) alkoxides could be regenerated from the tin oxide residues and reused, paving the way for a continuous industrial process. Extension of the scope to the synthesis of diurethanes from toluene 2,4-diamine and 4,4'-methylenedianiline could potentially allow the efficient production of industrially relevant diisocyanates.

Investigations on the catalytic carboxylation of olefins with CO2 towards α,ß-unsaturated carboxylic acid salts: characterization of intermediates and ligands as well as substrate effects.

The carboxylation of olefins beyond ethylene towards α,ß-unsaturated carboxylic acid salts and a detailed investigation on the critical steps in the catalysis are reported. The influence of two chelating phosphine ligands and several olefins on the elemental steps of the catalysis is shown. The work focusses on the formation of intermediate olefin complexes, lactone formation and base induced elimination of the lactone. The direct carboxylation of olefins is possible using nickel catalysts, which opens a new route towards the desired α,ß-unsaturated carboxylic acid salts. The reaction works particularly well for 1,3-dienes and proceeds via the formation of allyl-carboxylates. The ability to form such allyl-type lactone complexes seems in this case to be the most challenging step towards satisfactory turnover numbers.

Excited states with internally contracted multireference coupled-cluster linear response theory.

In this paper, the linear response (LR) theory for the variant of internally contracted multireference coupled cluster (ic-MRCC) theory described by Hanauer and Köhn [J. Chem. Phys. 134, 204211 (2011)] has been formulated and implemented for the computation of the excitation energies relative to a ground state of pronounced multireference character. We find that straightforward application of the linear-response formalism to the time-averaged ic-MRCC Lagrangian leads to unphysical second-order poles. However, the coupling matrix elements that cause this behavior are shown to be negligible whenever the internally contracted approximation as such is justified. Hence, for the numerical implementation of the method, we adopt a Tamm-Dancoff-type approximation and neglect these couplings. This approximation is also consistent with an equation-of-motion based derivation, which neglects these couplings right from the start. We have implemented the linear-response approach in the ic-MRCC singles-and-doubles framework and applied our method to calculate excitation energies for a number of molecules ranging from CH2 to p-benzyne and conjugated polyenes (up to octatetraene). The computed excitation energies are found to be very accurate, even for the notoriously difficult case of doubly excited states. The ic-MRCC-LR theory is also applicable to systems with open-shell ground-state wavefunctions and is by construction not biased towards a particular reference determinant. We have also compared the linear-response approach to the computation of energy differences by direct state-specific ic-MRCC calculations. We finally compare to Mk-MRCC-LR theory for which spurious roots have been reported [T.-C. Jagau and J. Gauss, J. Chem. Phys. 137, 044116 (2012)], being due to the use of sufficiency conditions to solve the Mk-MRCC equations. No such problem is present in ic-MRCC-LR theory.

Communication: Restoring full size extensivity in internally contracted multireference coupled cluster theory.

The reason for the lack of size extensivity in the valence space in current implementations of internally contracted multireference coupled cluster theories is the procedure used to eliminate redundant components from the cluster operator. We present a simple way to restore full size extensivity by performing this critical step in a basis of excitation operators that are normal ordered with respect to the multiconfigurational reference function.

Perturbative treatment of triple excitations in internally contracted multireference coupled cluster theory.

Internally contracted multireference coupled cluster (ic-MRCC) methods with perturbative treatment of triple excitations are formulated based on Dyall's definition of a zeroth-order Hamiltonian. The iterative models ic-MRCCSDT-1, ic-MRCC3, and their variants ic-MRCCSD(T), ic-MRCC(3) which determine the energy correction from triples by a non-iterative step are consistent in the single-reference limit with CCSDT-1a, CC3, CCSD(T), and CC(3), respectively. Numerical tests on the potential energy surfaces of BeH(2), H(2)O, and N(2) as well as on the structure and harmonic vibrational frequencies of the ozone molecule show that these methods account very well for higher order correlation effects. The ic-MRCCSD(T) method is further applied to the geometry optimization and harmonic frequencies of the symmetric vibrational modes of the binuclear transition metal oxide Ni(2)O(2), to the singlet-triplet splittings of o-, m-, and p-benzyne and to a ring-opening reaction of an azirine compound with the molecular formula C(6)H(7)NO. The size of the active spaces used in this study ranges from CAS(2,2) to CAS(8,8). Comparisons of results based on differently sized active spaces indicate that the ic-MRCCSD(T) method provides a highly accurate and efficient treatment of both static and dynamic electron correlation in connection with minimal active spaces.

A sequential transformation approach to the internally contracted multireference coupled cluster method.

The internally contracted multireference coupled cluster (ic-MRCC) approach is formulated using a new wave function ansatz based on a sequential transformation of the reference function (sqic-MRCC). This alternative wave function simplifies the formulation of computationally viable methods while preserving the accuracy of the ic-MRCC approach. The structure of the sqic-MRCC wave function allows folding the effect of the single excitations into a similarity-transformed Hamiltonian whose particle rank is equal to the one of the Hamiltonian. Consequently, we formulate an approximation to the sqic-MRCC method with singles and doubles (included respectively up to fourfold and twofold commutators, sqic-MRCCSD[2]) that contains all terms present in the corresponding single-reference coupled cluster scheme. Computations of the potential energy curves for the dissociation of BeH(2) show that the untruncated sqic-MRCCSD scheme yields results that are almost indistinguishable from the ordinary ic-MRCCSD method. The energy obtained from the computationally less expensive sqic-MRCCSD[2] approximation is found to deviate from the full ic-MRCCSD method by less than 0.2 mE(h) for BeH(2), while, in the case of water, the harmonic vibrational frequencies of ozone, the singlet-triplet splitting of p-benzyne, and the dissociation curve of N(2), sqic-MRCCSD[2] faithfully reproduces the results obtained via the ic-MRCCSD scheme truncated to two commutators. A formal proof is given of the equivalence of the ic-MRCC and sqic-MRCC methods with the internally contracted and full configuration interaction approaches.

Pilot applications of internally contracted multireference coupled cluster theory, and how to choose the cluster operator properly.

The internally contracted multireference coupled cluster (icMRCC) method allows a highly accurate description of both static and dynamic correlation with a computational scaling similar to single reference coupled cluster theory. The authors show that the method can lose its orbital invariance and size consistency when no special care is taken in the elimination of redundant excitations. Using the BeH(2) model system, four schemes are compared which differ in their treatment of linear dependencies between excitations of different rank (such as between singles and doubles). While the energy curves agree within tens of µE(h) when truncating the cluster operator at double excitations (icMRCCSD), inclusion of triple excitations (icMRCCSDT) leads to significant differences of more than 1 mE(h). One scheme clearly yields the best results, while the others even turn out to be not size consistent. The former procedure uses genuine single and double excitations and discards those linear combinations of (spectator) double and triple excitations which have the same effect on the reference function. With this approach, the equilibrium structure and harmonic vibrational frequencies of ozone obtained with icMRCCSDT are in excellent agreement with CCSDTQ. The authors further apply icMRCC methods to potential energy surfaces of HF, LiF, N(2), and to the singlet-triplet splitting of benzynes. In particular, the latter calculations have been made possible by implementing the method with the proper formal scaling using automated techniques.

Response properties with explicitly correlated coupled-cluster methods using a Slater-type correlation factor and cusp conditions.

The recently proposed extension of the explicitly correlated coupled-cluster ansatz using cusp conditions [A. Kohn, J. Chem. Phys. 130, 104104 (2009)] is tested for suitability in the calculation of response properties. For this purpose, static and dynamic electrical properties up to ESHG hyperpolarizabilities as well as optical rotations have been computed within the CCSD(F12) model. It is shown that effectively converged correlation contributions can reliably be obtained using augmented quadruple zeta basis sets already. The ansatz is optionally equipped with an extension capable of reducing the one-electron basis set error. A further simplification of the method specific Lagrangian aimed at reducing the computational effort has been tested and is shown to be uncritical. Furthermore, we examined the impact of conventional triple and quadruple excitations in explicitly correlated property calculations.

Tris(1,10-phenanthroline-kappa2N,N')cobalt(III) tris(trifluoromethanesulfonate) dihydrate.

The title compound, [Co(C(12)H(8)N(2))(3)](CF(3)SO(3))(3) x 2 H(2)O, crystallizes to form infinite chains of complex cations that are connected through offset face-to-face and edge-to-face interactions between their phenanthroline ligands. The chains are themselves interconnected through weak offset face-to-face ligand interactions. The three trifluoromethanesulfonate anions of the asymmetric unit are connected with one another through the two water molecules by hydrogen bonds. One of the trifluoromethanesulfonate anions is described by a disorder over three positions, with occupancies of 0.35, 0.35 and 0.3 in the refined model.

Separation of nanoparticles by gel electrophoresis according to size and shape.

We demonstrate the separation of gold and silver nanoparticles according to their size and shape by agarose gel electrophoresis after coating them with a charged polymer layer. The separation is monitored optically using the size- and shape-dependent plasmon resonance of noble metal particles and confirmed by transmission electron microscopy (TEM). Electrophoretic mobilities are quantitatively explained by a model based on the Henry formula, providing a theoretical framework for predicting gel mobilities of polymer coated nanoparticles.