We report a model describing the molecular orientation disorder in CH3NH3PbI3, solving a classical Hamiltonian parametrised with electronic structure calculations, with the nature of the motions informed by ab initio molecular dynamics. We investigate the temperature and static electric field dependence of the equilibrium ferroelectric (molecular) domain structure and resulting polarisability. A rich domain structure of twinned molecular dipoles is observed, strongly varying as a function of temperature and applied electric field. We propose that the internal electrical fields associated with microscopic polarisation domains contribute to hysteretic anomalies in the current-voltage response of hybrid organic-inorganic perovskite solar cells due to variations in electron-hole recombination in the bulk.

/pdf/molecular-ferroelectric-contributions-to-anomalous-49cagduwjj.pdf

Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells

Low‐frequency intermolecular dynamics in liquids is studied by ultrafast four‐ and six‐wave mixing. The theory of these nonlinear optical processes is given for electronically nonresonant optical interactions up to fifth order in the electric field. The Born–Oppenheimer approximation is used to separate the motional part of the response functions from coordinate independent electronic hyperpolarizabilities. A large variety of experiments, involving far‐infrared absorption, ordinary Rayleigh–Raman or hyper Rayleigh–Raman scattering is covered by this theory. The response in nonresonant six‐wave mixing comprises four dynamically different processes. It is shown that one of the terms contains information on the time scale(s) of intermolecular dynamics, that is not available from lower‐order nonresonant experiments. For instance, homogenous and inhomogeneous contributions to line broadening can be distinguished. The optical response of harmonic nuclear motion is calculated for nonlinear coordinate dependence of the polarizabilities. Results for level‐dependent and level‐independent damping of the motion are compared. It is shown that level‐dependent damping destroys the interference between different quantum mechanical pathways, yielding an extra contribution to the fifth‐order response that has not been discussed before. When two or more nuclear modes determine the optical response, their relative contributions to the four‐ and six‐wave mixing signals are in general different. These contributions are determined by the coordinate dependence of the electronic polarizability, which is usually not fully known. Model calculations are presented for the dynamic parameters of liquid CS2. The theory of this paper will be employed in Part II, to analyze experimental results on femtosecond four‐ and six‐wave mixing.

/pdf/time-resolved-four-and-six-wave-mixing-in-liquids-i-theory-51ty9m7i4u.pdf

Time resolved four‐ and six‐wave mixing in liquids. I. Theory

A nonholonomic system subjected to external noise from the environment, or internal noise in its own actuators, will evolve in a stochastic manner described by an ensemble of trajectories. This ensemble of trajectories is equivalent to the solution of a Fokker–Planck equation that typically evolves on a Lie group. If the most likely state of such a system is to be estimated, and plans for subsequent motions from the current state are to be made so as to move the system to a desired state with high probability, then modeling how the probability density of the system evolves is critical. Methods for solving Fokker-Planck equations that evolve on Lie groups then become important. Such equations can be solved using the operational properties of group Fourier transforms in which irreducible unitary representation (IUR) matrices play a critical role. Therefore, we develop a simple approach for the numerical approximation of all the IUR matrices for two of the groups of most interest in robotics: the rotation group in three-dimensional space, SO(3), and the Euclidean motion group of the plane, SE(2). This approach uses the exponential mapping from the Lie algebras of these groups, and takes advantage of the sparse nature of the Lie algebra representation matrices. Other techniques for density estimation on groups are also explored. The computed densities are applied in the context of probabilistic path planning for kinematic cart in the plane and flexible needle steering in three-dimensional space. In these examples the injection of artificial noise into the computational models (rather than noise in the actual physical systems) serves as a tool to search the configuration spaces and plan paths. Finally, we illustrate how density estimation problems arise in the characterization of physical noise in orientational sensors such as gyroscopes.

/pdf/kinematic-state-estimation-and-motion-planning-for-fz1ww2f8e2.pdf

Kinematic state estimation and motion planning for stochastic nonholonomic systems using the exponential map

/pdf/microwave-material-interactions-and-dielectric-properties-y43cc9ix1c.pdf

Microwave‐Material Interactions and Dielectric Properties, Key Ingredients for Mastery of Chemical Microwave Processes

The purpose of this paper is to enlighten by a theoretical analysis the controversial question of atnermul, specific or molecular effects of microwave heating claimed in chemistry.In this Part II, orienting effects of electric field, and physical origin of dielectric loss will be analyzed, as well as transfers between rotational states and vibrational states within condensed phases. We will formulate six criteria relating to existence of microwave athermal effects. In fact these criteria will look like some lemma leading then to the formulation of a general theorem relating to existence of molecular or athermal effects in micro valve heating. In the usual operating conditions, it will be proven that the frequently propounded idea that the microwaves rotate dipolar groups is misleading.

Microwave Athermal Effects in Chemistry: A Myth’s Autopsy: Part II: Orienting effects and thermodynamic consequences of electric field.

Spend your time even for only few minutes to read a book. Reading a book will never reduce and waste your time to be useless. Reading, for some people become a need that is to do every day such as spending time for eating. Now, what about you? Do you like to read a book? Now, we will show you a new book enPDFd rotational brownian motion and dielectric theory that can be a new way to explore the knowledge. When reading this book, you can get one thing to always remember in every reading time, even step by step.

Rotational Brownian motion and dielectric theory

Quantum Particle Dynamics

Low-energy experimental results for antiproton-proton annihilation are used to determine interaction volumes for pions and kaons. The information so obtained is utilised to make predictions for production of elementary particles, excluding isobars, for antiproton momenta 3GeV/c, 6GeV/c, 9.14GeV/c.

Covariant statistical treatment of antiproton annihilation

Multiplicities in weight diagrams.

Whittaker's studies of the relations between physics and philosophy are contained in about forty books and papers, nearly all of which were published during the last fifteen years of his life. His approach is mainly historical and is a natural sequence to his History of the Theories of Aether and Electricity . Many of the publications were based on lectures delivered to various groups and there is naturally a certain amount of repetition.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/FEA7E1591D8F8CCF5A32D458929C7630/S0013091500014383a.pdf/div-class-title-whittaker-s-correlation-of-physics-and-philosophy-div.pdf

Whittaker's Correlation of Physics and Philosophy

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