Beyond Continuum Solvent Models in Computational Homogeneous Catalysis

In homogeneous catalysis solvent is an inherent part of the catalytic system. As such, it must be considered in the computational modeling. The most common approach to include solvent effects in quantum mechanical calculations is by means of continuum solvent models. When they are properly used, average solvent effects are efficiently captured, mainly those related with solvent polarity. However, neglecting atomistic description of solvent molecules has its limitations, and continuum solvent models all alone cannot be applied to whatever situation. In many cases, inclusion of explicit solvent molecules in the quantum mechanical description of the system is mandatory. The purpose of this article is to highlight through selected examples what are the reasons that urge to go beyond the continuum models to the employment of micro-solvated (cluster-continuum) of fully explicit solvent models, in this way setting the limits of continuum solvent models in computational homogeneous catalysis. These examples showcase that inclusion of solvent molecules in the calculation not only can improve the description of already known mechanisms but can yield new mechanistic views of a reaction. With the aim of systematizing the use of explicit solvent models, after discussing the success and limitations of continuum solvent models, issues related with solvent coordination and solvent dynamics, solvent effects in reactions involving small, charged species, as well as reactions in protic solvents and the role of solvent as reagent itself are successively considered.

On the Quantum Mechanical Description of the Interaction between Particle and Detector

Quantum measurements of physical quantities are often described as ideal measurements. However, only a few measurements fulfil the conditions of ideal measurements. The aim of the present work is to describe real position measurements with detectors that are able to detect single particles. For this purpose, a detector model is developed that can describe the time dependence of the interaction between a non-relativistic particle and a detector. The example of a position measurement shows that this interaction can be described with the methods of quantum mechanics. At the beginning of a position measurement, the detector behaves as a target consisting of a large number of quantum mechanical systems. In the first reaction, the incident particle interacts with a single atom, electron or nucleus, but not with the whole detector. This reaction and all following reactions are quantum mechanical processes. At the end of the measurement, the detector can be considered as a classical apparatus. A detector is neither a quantum mechanical system nor a classical apparatus. The detector model explains why one obtains a well-defined result for each individual position measurement. It further explains that, in general, it is impossible to predict the outcome of an individual measurement.

Polishing of precision parts of optical-electronic and laser equipment

The mechanism of interaction of the optical surface with the polishing dispersed system during polishing is investigated. It is established that the energy transfer between them is a consequence of the dipole-dipole interaction in the donor-acceptor system and occurs by the Ferster mechanism. It was found that the decrease in the spectral separation between the treated material and the particles of polishing powder causes an increase in the size of sludge particles and wear particles, which leads to an increase in the roughness parameters Ra, Rq, Rmax of optical surfaces during polishing by polishing dispersed sys-tems. It is shown that the polishing productivity of optical surfaces and the wear intensity of polishing powder particles decrease with increasing corresponding transfer energies, which confirms the main pro-visions of the cluster theory of polishing of nonmetallic materials and the validity of quantum mechanical description of resonant energy transfer mechanism between dispersed material and dispersed system.

Color confinement at the boundary of the conformally compactified AdS5

The topology of closed manifolds forces interacting charges to appear in pairs. We take advantage of this property in the setting of the conformal boundary of AdS5 spacetime, topologically equivalent to the closed manifold S1× S3, by considering the coupling of two massless opposite charges on it. Taking the interaction potential as the analog of Coulomb interaction (derived from a fundamental solution of the S3 Laplace-Beltrami operator), a conformal S1× S3 metric deformation is proposed, such that free motion on the deformed metric is equivalent to motion on the round metric in the presence of the interaction potential. We give explicit expressions for the generators of the conformal algebra in the representation induced by the metric deformation.By identifying the charge as the color degree of freedom in QCD, and the two charges system as a quark-anti-quark system, we argue that the associated conformal wave operator equation could provide a realistic quantum mechanical description of the simplest QCD system, the mesons.Finally, we discuss the possibility of employing the compactification radius, R, as an- other scale along ΛQCD, by means of which, upon reparametrizing Q2c2 as (Q2c2+ħ2c2/R2), a perturbative treatment of processes in the infrared could be approached.

Mössbauer experiments in a rotating system and physical interpretation of their results

We discuss the results of modern Mössbauer experiments in a rotating system, which show the presence of an extra energy shift between the emitted and absorbed resonant radiation in addition to the relativistic energy shift of the resonant lines due to the time dilation effect in the co-rotating source and absorber with different radial coordinates. We analyse the available attempts to explain the origin of the extra energy shift, which include some extensions of special theory of relativity with hypothesis about the existence of limited acceleration in nature, with hypothesis about a so-called «time-dependent Doppler effect», as well as in the framework of the general theory of relativity under re-analysis of the metric effects in the rotating system, which is focused to the problem of correct synchronisation of clocks in a rotating system with a laboratory clock. We show that all such attempts remain unsuccessful until the moment, and we indicate possible ways of solving this problem, which should combine metric effects in rotating systems with quantum mechanical description of resonant nuclei confined in crystal cells.

Computation is Existence — A Brief Overview of the Multi-faceted Implications of Quantum Mechanical Description of Black holes as hyper computational Entities

The article attempts to deal with the newly emerging paradigm of black hole computers in which adopting a quantum-mechanical perspective of information enables us to assess the computational power of black holes. Viewing space-time itself as a computational entity and black holes as the supreme forms of serial computers can help us to gain insight into the ideas from gravitational thermodynamics and the emergent nature of space-time and gravity. The idea of black holes as computational entities also relates to quantum gravity which views space-time and foamy and fuzzy due to quantum fluctuations and divided into discrete, Planck-scale blocks.

“Inverted” CO molecules on NaCl(100): a quantum mechanical study

Inverted (“O-down”) CO adsorbates on NaCl(100), recently observed experimentally after IR vibrational excitation (Lau et al., Science, 2020, 367, 175–178), are characterized using periodic DFT and a quantum mechanical description of vibrations.

Quantum defect and common fractions

The common fractions N1/N2, where N1 and N2 - the small integers, quite often are used at the quantum-mechanical description of microcosm objects (for example, fractional charges of quarks and some quantum characteristics, such as particles spin). Recently the fractional quantum Hall effect was discovered, and common fractions have considerably expanded their presence in microcosm physics. The theory of the fractional quantum Hall effect has appeared nontrivial, so the Nobel Prize on physics in 1998 was awarded not only for discovery of the effect in 1982 (Daniel Tsui and Horst Störmer) but also for the theory creation in 1983 (Robert Laughlin). And now one more sensational discovery: common fractions were «detected» at the analysis of experimental characteristics of «hydrogen-like» atoms and ions (with only one electron on an outer shell). It has appeared, that the effective main quantum number of outer shell electron, that is, subject to quantum defect (Rydberg correction), can be expressed in common fractions.

Failure of Molecular Dynamics to Provide Appropriate Structures for Quantum Mechanical Description of the Aqueous Chloride Ion Charge-Transfer-to-Solvent Ultraviolet Spectrum

The lowest band in the experimental charge-transfer-to-solvent ultraviolet absorption spectrum of aqueous chloride ion is studied by experiment and computation. Interestingly, the experiments indicate that at concentrations up to at...

Bit from Qubit. A Hypothesis on Wave-Particle Dualism and Fundamental Interactions

In this article a completely objective decoherence mechanism is hypothesized, operating at the level of the elementary particles of matter. The standard quantum mechanical description is complemented with a phenomenological evolution equation, involving a scalar curvature and an internal time, distinct from the observable time of the laboratory. This equation admits solutions internal to the wave function collapse, and the classical instantons connected to these solutions represent de Sitter micro-spaces identifiable with elementary particles. This result is linked in a natural way to other research programs tending to describe the internal structure of elementary particles by means of de Sitter spaces. Both the possible implications in particle physics and those deriving from the conversion of quantum information (qubits) into classical information (bits) are highlighted.