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High power application of Li‐battery remains a challenge due to the lack of stable fast‐charging cathode materials. Lithium manganese oxide (LMO) cathode is very promising due to its high operating voltage and fast charging ability; however, the associated Mn‐dissolution is one of the main hindrances to its practical applicability. In this work, we demonstrate for the first time the use of a commercially scalable method through a proprietary Calix flash calcination (CFC) technology to develop high‐performance electrode materials where a novel CXL LMO material was manufactured and tested. CXL LMO|Li metal cell showed a reversible specific capacity of 110 mAh/g with 99 % retention after 100 cycles and showed excellent rate performance up to 20 C current rate (~20 mA/cm2 current density). CXL LMO|Graphite cell (areal capacity 1 mAh/cm2) was also reported with 86 % capacity retention over more than 500 cycles. Cross‐section morphology revealed a unique multi‐layered structure that was retained at the core of the novel LMO material. It obtained lesser Mn dissolution compared to commercial LMO. The scalable synthesis procedure through CFC technology, can be broadly applicable to produce unique electrode morphology as demonstrated here for the CXL LMO representing a promising pathway for electrode manufacturing for high‐power Li‐batteries. [ABSTRACT FROM AUTHOR]

A time-local Fokker–Planck equation (TLFPE) is derived which accounts for memory effects in stochastic problems. This is expected to provide a computationally efficient method of modeling the phase space evolution of such systems by simple (local time) Langevin equations with Markovian fluctuating forces that are characterized by time-dependent moments; it is this explicit time dependence that describes the memory effects. The TLFPE is derived from the probability theory of non-Markovian systems as a generalization of Chandrasekar’s derivation of the Fokker–Planck equation (FPE) from the Chapman–Kolmogarov equation for Markovian systems. In this article it is applied to free particle diffusion and barrier crossing problems, and is shown to give rise to physically realistic results. Further, the form of the TLFPE suggests that the conditions required for systems to exhibit Markovian behavior are less restrictive than the Brownian criterion of separation of time scales between the fluctuating forces and the momentum response of the system. Rather, a sufficient condition is that the time-dependent moments of the TLFPE reach plateau values before the time scale of the phenomenon of interest. [ABSTRACT FROM AUTHOR]

The atom–atom encounter model for collisional energy transfer by monatomic colliders previously developed for diatomics [M.G. Sceats, Chem. Phys. Lett. 151, 281 (1988)] is extended to polyatomic molecules. For small molecules, such as triatomics, the density of states is sufficiently low at high energies that the result can be enumerated for each state. For large polyatomics a statistical approach based on either microcanonical or effective canonical distributions can be used when independent degrees of freedom are assumed. An effective anharmonicity at high energy is incorporated by inclusion of diagonal terms for these independent degrees of freedom. The primary feature of the model is that it accounts for kinematic effects, such as momentum transfer efficiency and the adiabatic nature of collisions, which are not accounted for in ergodic theories of energy transfer. [ABSTRACT FROM AUTHOR]

The atom–atom encounter model developed in the accompanying paper [M. G. Sceats, J. Chem. Phys. 91, 0000 (1989)] is applied to the collisional deactivation of highly vibrationally excited triatomic molecules CS2 and SO2 by the monatomic colliders He, Ne, Ar, Kr, and Xe at 300 K. The molecular inputs are a crude normal mode analysis, vibrational frequencies and effective anharmonicities, while the collisional inputs are parameters of the atom–atom potentials. The results for CS2 are compared with the simulations of Bruehl and Schatz and the experiments of Dove, Hippler, and Troe, while those for SO2 are compared with the simulations of Schranz and Troe and the experimental results of Heymann, Hippler, and Troe. Excellent agreement is found with experiment, and the superlinear energy dependence of the average energy transfer is attributed to anharmonicity of the triatomic molecule. [ABSTRACT FROM AUTHOR]

The Hamiltonian-based model developed by the authors [N. J. Cotes and M. G. Sceats, J. Chem. Phys. 89, 2816 (1988)] for bimolecular reactions which exhibit severe configurational restrictions, such as orientational requirements for reaction at surface sites, provides an analytical expression for the reaction rate which involves the evaluation of the potential of mean force along the radial coordinate that describes the binding. The expression for the reaction rate is evaluated for the case of a charged molecule interacting with a binding site on a dipolar particle. The results of the model are compared with the multidimensional Brownian-dynamics simulations of Northrup et al. [J. Chem. Phys. 84, 5536 (1986)] and excellent agreement is obtained in the diffusion limit. [ABSTRACT FROM AUTHOR]

A theory is developed of the dependence of the steady-state electron–ion pair recombination rate constant on the electron mean free path. The problem, in classical mechanics, is reduced to the stochastic dynamics of the electron in the one-dimensional effective potential V(R)=-kTRc/R -2kT ln R. Rc is the Onsager length Ze2/4πεkT. For a large mean free path λ, the recombination rate is determined by energy relaxation of electrons which cross the transition state of V(R) at RT=Rc/2, whereas for small λ the Debye result for spatial diffusion-controlled recombination is obtained. The theory gives the dependence of the rate in the crossover regime where λ is comparable to Rc. The results are in good agreement with experiment and Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The steady state rate constant for passage over a fluctuating potential barrier is derived from the Fokker–Planck equation using the stable states picture. The time scale of fluctuations in barrier height and position do not influence the reactive frequency; however, the reactive frequency does depend upon the time scale of fluctuations in the barrier curvature. If these are fast relative to [ω2m+(ξ/2)2]1/2, where ωm is the mean barrier frequency and ξ is the friction for motion along the reaction coordinate, then the crossing takes place on the potential of mean force. If the barrier fluctuations are slow on the same time scale, then the rate is an average over that for the distribution of barriers. In both of these limits the form of the Kramers solutions is recovered, whereas in the intermediate case, the rate also depends explicitly on the relaxation time scale of the fluctuations. A physically reasonable model for the decay of fluctuations in the potential is proposed and used to obtain an analytic expression for the rate that covers the range between these two limits. [ABSTRACT FROM AUTHOR]

A formulation is presented for the bimolecular reaction rate between a small reactant molecule A in bulk with a reactive site B on the surface of a large particle E. The approach allows a direct comparison of this rate with that between A and B in bulk. The direct interaction potential between A and B is modeled by a central force potential VAB(R) which is assumed to be unchanged upon binding of B. The reaction rate is evaluated by reduction of the problem to a one-dimensional barrier crossing problem on the effective potential V(R)=V(R)-kT ln[ f (R)], where the entropic term accounts for the constraints of binding on the surface. The solution applies for arbitrary mean free path, and its limits are applicable to reactions in solutions (diffusion regime) and in gas phase (free molecule regime). [ABSTRACT FROM AUTHOR]

A molecular model of self-diffusion in an atomic fluid is developed and tested against hard sphere simulation results. The model is based on a variation of Kirkwood’s theory of friction and a theory of binary encounters of Sceats. The model uses characteristics of the potential of mean force to characterize the deviation of D from Enskog theory DE as the density increases. At intermediate density D/DE exceeds unity because of the reduction of flux of binary encounters caused by third body collisions and at high density this effect is overwhelmed by the enhancement of the zero frequency value of the force power spectrum due to three center force correlations. Fluctuations in local structure are important at densities where caging becomes important. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are reported for a solute immersed in a monatomic solvent; systems modeled represent monatomic and diatomic solute species (whose atoms are larger and heavier than the solvent), with varying force constant and bond length for the diatomic. From these simulations, autocorrelation functions, diffusion coefficients (D), and friction coefficients (ξ) are determined; for the diatomic, these are found for both the center-of-mass and relative coordinates. These results are used to develop simple models for D and ξ, including (for the diatomic relative coordinate) their frequency dependence. The models enable D and ξ to be readily determined from properties such as bulk viscosity, potential parameters, etc. These D and ξ can be used to interpret and predict picosecond time scale data for solute dynamics using stochastic models (e.g., the Kramers or Langevin equations) at the molecular level; their theoretical basis is such that they should apply to many types of solute moieties (e.g., aromatic rings) as well as to the large atoms used in the simulations. [ABSTRACT FROM AUTHOR]

The bimolecular reaction rate of molecules constrained to a surface is obtained in a simple form. The solution applies for any central force potential and for arbitrary mean free path, giving in the limit of high friction the solution to the diffusion equation with its logarithmic dependence on surface density and in the limit of low friction the result of canonical variational transition state theory. [ABSTRACT FROM AUTHOR]

A model of the initial kinetics of cyclization and ring opening of a polymer is developed using a generalized Langevin approach. The model reduces the complex problem to a simpler one of evaluating the dynamics of passage over a transition state in the one-dimensional effective potential of mean force deduced from a superposition of the end-segment binding potential and the end-segment distribution function for unreactive end segments. The model accounts not only for the short range binding, but also for the long range excluded volume and hydrodynamic interactions. It is shown how the initial rates of the theory, and the steady state of cyclization rate of Wilemski–Fixman–Doi theory combine to give the cyclization kinetics over the entire time domain. Expressions for the evolution of the yields of cyclized and linear polymers have been obtained. These include the fluorescence decay times for use in experiments which use such probes. [ABSTRACT FROM AUTHOR]

The N-particle Fokker–Planck equation has been cast into a form which is invariant to coordinate transformations. For a pair of particles interacting through a radial potential V(R), the equation of motion may be projected onto a one-dimensional problem in R when the conjugate momenta of the center of mass and internal coordinates have symmetric distributions, as in Boltzmann distributions. However, the R2 dependence of the density of configuration space demands that V(R) be supplemented with an effective repulsive potential -2kT ln R, a result which has consequences for Langevin simulations of chemical processes. For N interacting particles a subset of coordinates can often be identified as having such symmetric distributions, and if these are not of interest, they can be eliminated with the result that the potential containing the remaining coordinates is supplemented by -kT ln(|gkl|)1/2, where |gkl| is the determinant of that portion of the covariant metric tensor pertaining to unwanted coordinates k and l. [ABSTRACT FROM AUTHOR]

The extant experimental data for the n-alkanes (pentane–hexadecane) derived from ultrasonic absorption, Brillouin and Rayleigh light scattering, and low frequency shear viscosity measurements are analyzed in terms of a model which decomposes the frequency dependent shear and longitudinal viscosities into contributions arising from trans–gauche rotational isomerism, rotational reorientation, and structural relaxation. The results yield values of the transverse and longitudinal structural relaxation times, and indicate that there is a strong coupling of molecular reorientation to adiabatic compression as well as to shear, presumably because the existing orientational correlations between chains are perturbed by the temperature variations during adiabatic compression. [ABSTRACT FROM AUTHOR]

Measurements of the in-phase collective OH stretching band in the Raman spectrum of H2O/H2O2 mixtures have been carried out over a wide range of compositions and temperatures. At low mole fractions (<0.08) H2O2 introduces defects into the tetrahedral network of the water molecules, whereas at higher concentrations the behavior is interpreted in terms of a reduction of the vibron bandwidth resulting from reconstruction of the hydrogen bond network to one of lower average coordination. [ABSTRACT FROM AUTHOR]

The Fokker–Planck equation for two particles, when reduced to a one-dimensional problem in the radial coordinate, yields a transition state in the effective potential V(R)-2kT ln(R/R’) for potentials exhibiting capture characteristics. Application of Kramers solution to barrier crossing yields an analytic formula for the capture rate constant which applies for all particle sizes relative to the bath mean free path, giving the exact result for large particles for diffusion on V(R) and the kinetic theory result for small particles. The influence of the potential is accounted for by two stability factors W(0) and W(∞). For hard spheres the results are in good agreement with extant theory. Extension to include hydrodynamic interaction and relaxation is indicated. [ABSTRACT FROM AUTHOR]