We introduce a coarse-grained simulation model for the reductive deposition of lithium cations in secondary lithium metal batteries. The model accounts for the heterogeneous and nonequilibrium nature of the electrodeposition dynamics, and it enables simulation of the long timescales and lengthscales associated with metal dendrite formation. We investigate the effects of applied overpotential and material properties on earlystage dendrite formation, as well as the molecular mechanisms that govern this process. The model confirms that dendrite formation propensity increases with the applied electrode overpotential, and it demonstrates that application of the electrode overpotential in time-dependent pulses leads to dramatic suppression of dendrite formation while reducing the accumulated electrode on-time by as much as 96%. Moreover, the model predicts that time dependence of the applied electrode overpotential can lead to positive, negative, or zero correlation between cation diffusivity in the solid−electrolyte interphase (SEI) and dendrite formation propensity. Analysis of the simulation trajectories reveals that dendrite formation emerges from a competition between the timescales for cation diffusion and reduction at the anode/SEI interface, with lower applied overpotentials and shorter electrode pulse durations shifting this competition in favor of lower dendrite formation propensity. This work provides a molecular basis for understanding and designing pulsing waveforms that mitigate dendrite formation while minimally affecting battery charging times.

Here we develop a microscopic approach aimed at the description of a suite of physical effects related to carrier transport in, and the optical properties of, halide perovskites. Our theory is based on the description of the nuclear dynamics to all orders and goes beyond the common assumption of linear electron-phonon coupling in describing the carrier dynamics and band gap characteristics.When combined with first-principles calculations and applied to the prototypical MAPbI3 system, our theory explains seemingly disparate experimental findings associated with both the chargecarrier mobility and optical absorption properties, including their temperature dependencies. Our findings demonstrate that orbital overlap fluctuations in the lead-halide structure plays a significant role in determining the optoelectronic features of halide perovskites.

Ground state diffusion Monte Carlo is used to investigate the binding energies and carrier probability distributions of excitons, trions, and biexcitons in a variety of two-dimensional transition metal dichalcogenide materials. We compare these results to approximate variational calculations, as well as to analogous Monte Carlo calculations performed with simplified carrier interaction potentials. Our results highlight the successes and failures of approximate approaches as well as the physical features that determine the stability of small carrier complexes in monolayer transition metal dichalcogenide materials. Lastly, we discuss points of agreement and disagreement with recent experiments.

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A new cumulant-based GW approximation for the retarded one-particle Green's function is proposed, motivated by an exact relation between the improper Dyson self-energy and the cumulant generating function. Qualitative aspects of this method are explored within a simple one-electron independent phonon model, where it is seen that the method preserves the energy moment of the spectral weight while also reproducing the exact Green's function in the weak coupling limit. For the three-dimensional electron gas, this method predicts multiple satellites at the bottom of the band, albeit with inaccurate peak spacing. However, its quasiparticle properties and correlation energies are more accurate than both previous cumulant methods and standard G 0 W 0 . Our results point to new features that may be exploited within the framework of cumulant-based methods and suggest promising directions for future exploration and improvement of cumulant-based GW approaches.

A fully microscopic model of the doping-dependent exciton and trion linewidths in the absorption spectra of monolayer transition metal dichalcogenides in the low temperature and low-doping regime is explored. The approach is based on perturbation theory and avoids the use of phenomenological parameters. In the low-doping regime, we find that the trion linewidth is relatively insensitive to doping levels, while the exciton linewidth increases monotonically with doping. On the other hand, we argue that the trion linewidth shows a somewhat stronger temperature dependence. The magnitudes of the linewidths are likely to be masked by phonon scattering for T ≥ 20 K in encapsulated samples in the low-doping regime. We discuss the breakdown of perturbation theory, which should occur at relatively low-doping levels and low temperatures. Our work also paves the way toward understanding a variety of related scattering processes, including impact ionization and Auger scattering in clean 2D samples.

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