Quantum Theory Research Articles

Levamisole Based Co(II) Single-Ion Magnet.

A new Co(II) complex, [Co(NCS)2(L)2] (1) has been synthesized based on levamisole (L) as a new ligand. Single-crystal X-ray diffraction analyses confirm that the Co(II) ion is having a distorted tetrahedral coordination geometry in the complex. Notably strong intramolecular S⋅⋅⋅S and S⋅⋅⋅N interactions has been confirmed by employing Quantum Theory of Atoms in Molecules (QTAIM). These intramolecular interactions occur among the sulfur and nitrogen atoms of the levamisole ligands and also the nitrogen atoms of the thiocyanate. Direct current (dc) magnetic analyses reveal presence of zero field splitting (ZFS) and large magnetic anisotropy on Co(II). Detailed ab initio ligand field theory calculations quantitatively predicted the magnitude of ZFS. Prominent field-induced single-ion magnet (SIM) behavior was observed for 1 from dynamic magnetization measurements. Slow magnetic relaxation follows an Orbach mechanism with the effective energy barrier Ueff=29.6 (7) K and relaxation time τo=1.4 (4)×10-9 s.

Contributions of K. R. Parthasarathy (KRP) to Mathematics of Quantum theory - Perturbations of Operators and Quantum Stochastic Calculus

Contributions of K. R. Parthasarathy (KRP) to Mathematics of Quantum theory - Perturbations of Operators and Quantum Stochastic Calculus

Revisiting Dynamics of Quantum Causal Structures-When Can Causal Order Evolve?

Recently, there has been substantial interest in studying the dynamics of quantum theory beyond that of states, in particular, the dynamics of channels, measurements, and higher-order transformations. Castro-Ruiz et al. pursues this using the process-matrix formalism, together with a definition of the possible dynamics of such process matrices, and focusing especially on the question of evolution of causal structures. One of its major conclusions is a strong theorem saying that within the formalism, under continuous and reversible transformations, the causal order between operations must be preserved. Our result here challenges that of Castro-Ruiz et al.: if one is to take into account a full picture of the physical evolution of operations within the standard quantum-mechanical formalism, then the conclusion of Castro-Ruiz et al. does not hold. That is, we show that under certain continuous and reversible dynamics, the causal order between operations is not necessarily preserved. We moreover identify and analyse the root of this apparent contradiction, specifically, that the commonly accepted and widely applied framework of higher-order processes, whilst mathematically sound, is not always appropriate for drawing conclusions on physical dynamics. Finally, we show how to reconcile the elements of the whole picture following the intuition based on entanglement processing by local operations and classical communication.

The Perfluoro-o-phenylene-mercury Trimer [Hg(o-C6F4)]3 - a Textbook Example of Phase-Dependent Structural Differences.

The geometric and electronic structure of [Hg(o-C6F4)]3 (1) in the gas phase, i. e. free of intermolecular interactions, was determined by a synchronous gas-phase electron diffraction/mass spectrometry experiment (GED/MS), complemented by quantum chemical calculations. 1 is stable up to 498 K and the gas phase contains a single molecular form: the trimer [Hg(o-C6F4)]3. It has a planar structure of D3h symmetry with a Hg-C distance of 2.075(5) Å and a Hg-Hg distance of 3.614(7) Å (both rh1). Structural differences between the crystalline and gaseous state have been analyzed. Different DFT functional-basis combinations were tested, demonstrating the importance to consider the relativistic effects of the mercury atoms. The combination PBE0/MWB(Hg),cc-pVTZ(C,F) turned out to be the most appropriate for the geometry optimization of such organomercurials. The electronic structure of 1, the nature of the chemical bonding in C-Hg-C fragments and the nature of the Hg⋅⋅⋅Hg interactions have been analyzed in terms of the Natural Bond Orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) approaches. The influence of the nature of halogen substitution on the structure of the molecules in the series [Hg(o-C6H4)]3, [Hg(o-C6F4)]3, [Hg(o-C6Cl4)]3, [Hg(o-C6Br4)]3 was also analyzed.

Unveiling spectroscopic behaviour and molecular features (DFT studies) of Exemestane-maleic acid cocrystal as model multicomponent system

The present study aimed to investigate the Exemestane - maleic acid (Ex-Mal) cocrystal using Fourier-transform Raman (FT-Raman), Fourier-transform Infrared (FT-IR), Powder X-ray Diffraction (PXRD) and Differential Scanning Calorimeter (DSC) experimental techniques and quantum chemical calculations. Exemestane (Ex) is an irreversible aromatase inhibitor, clinically used for the treatment of postmenopausal women having primary or advanced breast cancer. Maleic acid (Mal), a dicarboxylic acid is found in many vegetables and fruits and is used as a food additive and sweetener. Solution crystallization of Ex and Mal was done in the generation of Ex-Mal cocrystal (1:1). PXRD and DSC analysis confirmed the successful generation of Ex-Mal Cocrystal. Intermolecular hydrogen bonding (O4-H12···O13 & C8-O3···H36) also suggested the formation of a multi-component system, Ex-Mal cocrystal (1:1), as the respective modes shifted in the vibrational (Raman & IR) spectra of cocrystal than the Ex. Further, the quantum theory of atoms in molecules (QTAIM) has been done to analyze the strength and nature of inter-/intra molecular hydrogen bonding. Natural bond orbital (NBO) analysis was performed to check the stabilization energy of the system. The frontier molecular orbital (FMO) analysis predicted that Ex-Mal cocrystal is more reactive and less stable than Ex. Molecular electrostatic potential (MEP) surface showed that electrophilic (C16-H36)/(O4-H12), and nucleophilic (C8=O3)/(C17=O13) reactive groups in Ex/Mal and Mal/Ex, respectively, neutralized after the formation of Ex-Mal cocrystal, confirming the presence of hydrogen bonding interactions (C16-H36∙∙∙O3=C8) and (C17=O13∙∙∙H12-O4). Molar Refractivity (MR) was calculated to check the drug-likeness behaviours of Ex-mal cocrystal. This study provided a comparison of experimental and theoretical results to understand the hydrogen bonding interactions and structural activity of the system.

Relativistic scalar fields canonical quantization in Einstein–Yang–Mills–Higgs’s rotating black hole space-time

The quantum theory of relativistic mechanics to deal with the scalar fields behavior in a curved space-time is represented by the Klein–Gordon equation. In this work, we will investigate the gravitationally bound states of massive and massless scalar fields around a Einstein–Yang–Mills–Higgs’s rotating black hole. After applying the standard separation of variables ansatz, we will show in detail how to obtain the novel exact solutions of the radial part of the governing Klein–Gordon equation and express the radial solution in terms of the Confluent Heun functions. By applying the bound state boundary conditions, the Confluent Heun functions are reduced to be polynomials that lead to energy quantization. We find that the scalar fields have complex-valued energy levels that indicate the decaying/growing bound states known as quasibound states. In the end, using the exact radial solution, we derive the radiation distribution function of the black hole’s outer horizon to obtain the equation of the Hawking temperature.

Graviton Physics: A Concise Tutorial on the Quantum Field Theory of Gravitons, Graviton Noise, and Gravitational Decoherence

The detection of gravitational waves in 2015 ushered in a new era of gravitational wave (GW) astronomy capable of probing the strong field dynamics of black holes and neutron stars. It has opened up an exciting new window for laboratory and space tests of Einstein’s theory of classical general relativity (GR). In recent years, two interesting proposals have aimed to reveal the quantum nature of perturbative gravity: (1) theoretical predictions on how graviton noise from the early universe, after the vacuum of the gravitational field was strongly squeezed by inflationary expansion; (2) experimental proposals using the quantum entanglement between two masses, each in a superposition (gravitational cat, or gravcat) state. The first proposal focuses on the stochastic properties of quantum fields (QFs), and the second invokes a key concept of quantum information (QI). An equally basic and interesting idea is to ask whether (and how) gravity might be responsible for a quantum system becoming classical in appearance, known as gravitational decoherence. Decoherence due to gravity is of special interest because gravity is universal, meaning, gravitational interaction is present for all massive objects. This is an important issue in macroscopic quantum phenomena (MQP), underlining many proposals in alternative quantum theories (AQTs). To fully appreciate or conduct research in these exciting developments requires a working knowledge of classical GR, QF theory, and QI, plus some familiarity with stochastic processes (SPs), namely, noise in quantum fields and decohering environments. Traditionally a new researcher may be conversant in one or two of these four subjects: GR, QFT, QI, and SP, depending on his/her background. This tutorial attempts to provide the necessary connective tissues between them, helping an engaged reader from any one of these four subjects to leapfrog to the frontier of these interdisciplinary research topics. In the present version, we shall address the three topics listed in the title, excluding gravitational entanglement, because, despite the high attention some recent experimental proposals have received, its nature and implications in relation to quantum gravity still contain many controversial elements.

Rationalizing the stability and noncovalent interactions of N-(benzo[d][1,3]dioxol-5-ylmethyl)-2-(methylthio)thiazole-4-carboxamide: Insights from X‐ray structure and QTAIM analysis

A novel thiazole derivative, N-(benzo[d][1,3]dioxol-5-ylmethyl)-2-(methylthio)thiazole-4-carboxamide was synthesized and the structural interpretations were accomplished unambiguously by single crystal X-ray diffraction study. Structure investigation revealed that the crystal packing is stabilized by CH…N, and NH…O intermolecular interactions. Hirshfeld surface analysis used to explore the quantitative details of noncovalent interactions which are responsible for the crystal packing. The 3D energy framework, interaction energies and lattice energy of the compound were computed. Density functional theory (DFT) calculation was also employed to study various physicochemical properties of the compound. Quantum theory of atoms in molecules (QTAIM) analysis have been performed to study the intra and intermolecular interactions present in the thiazole derivative and also validate with the experimental results.

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications.

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

Quintessential f(G) gravity with statistically fitting of H(z)

Inspired by high-energy physics and by considering standard gravity theory as the low-energy limit of quantum theory, the modification of general relativity as [Formula: see text] has been proposed. This paper is dedicated to investigating the cosmological model of modified Gauss–Bonnet gravity in four dimensions. General field equations for the four-dimensional Friedmann– Robertson–Walker metric are given in detail. Also, it is well known that Hubble parameter [Formula: see text] measurements are helpful for the inference of cosmological model parameters. We try to explain the MCMC statistical approach used to calculate Hubble’s parameter. The resulting form of [Formula: see text] was limited using Cosmic Chronometric data, Standard Candles SN Ia from Pantheon, and Baryon Acoustic Oscillations to obtain the best match values by using the regression equation. Finally, to examine the late-time dynamics of our Universe, the behavior of physical and kinematic variables like the deceleration parameter [Formula: see text], State-finder parameters [Formula: see text], diagnostic parameter ([Formula: see text]), equation of state parameter as well as the behavior of energy conditions versus redshift with the parameter values are presented.

Hawking Temperature Modification and the Physical Dynamics of Black Holes: A Study of the Influence of Internal and Cosmological Variables

<p>The main objective of the study is to develop a model that modifies the traditional Hawking temperature by considering the influence of internal variables such as radius, mass, electric charge, angular momentum, and cosmological constant. The research method involves mathematical analysis and computational modeling based on the modified Hawking temperature equation. The results show that the modified Hawking temperature produces non-linear corrections that show the interaction between black holes and the quantum structure of spacetime. graphical representations visualize the variation of Hawking temperature with changes in area, electric charge, angular momentum, and cosmological parameters. The implications of the research extend to the understanding of the thermal properties of black holes in the context of gravitational and quantum theories. The research identifies gaps in the knowledge of the effects of cosmological parameters on black hole thermodynamics and introduces Hawking temperature modifications that have not been mapped in detail before. The study concludes that the Hawking temperature modification provides a strong foundation for further research in black hole physics, particularly in the effect of physical and cosmological parameters on the thermal properties of black holes.</p>

Tetrel Bond Affects the Self-Assembly of Acetylcholine and its Analogues and is an Ancillary Interaction in Protein Binding.

The -N+(CH3)3 residue is present in acetylcholine (ACh) and in many of its analogues which are used as selective ACh agonist or antagonists for human therapy. The X-ray structures of four ACh derivatives show the presence of short and linear contacts between the C atoms of -N+(CH3)3 groups and lone pair possessing atoms. These contacts can be rationalized as tetrel bonds (TtBs) thanks to their geometric features. Interrogation of the Protein Data Bank suggests that similar -N+-C⋅⋅⋅nucleophile contacts affect the details of the binding of ACh and its derivatives to proteins. Quantum theory of atoms in molecules, noncovalent interaction plot, and natural bond orbital analyses consistently confirm that the -N+-C⋅⋅⋅nucleophile contacts observed in small molecule crystals and in substrate/protein complexes are attractive in nature and can be rationalized as TtBs. TtBs involving methyl groups of the -N+(CH3)3 moiety can be proposed as a new item in the palette of interactions allowing the compounds containing this pharmacophoric unit to bind to their target protein and/or to express their biological/pharmacological properties.

The quantum Gaussian-Schell model: a link between classical and quantum optics.

The quantum theory of the electromagnetic field uncovered that classical forms of light were indeed produced by distinct superpositions of nonclassical multiphoton wave packets. This situation prevails for partially coherent light, the most common kind of classical light. Here, for the first time, to our knowledge, we demonstrate the extraction of the constituent multiphoton quantum systems of a partially coherent light field. We shift from the realm of classical optics to the domain of quantum optics via a quantum representation of partially coherent light using its complex-Gaussian statistical properties. Our formulation of the quantum Gaussian-Schell model (GSM) unveils the possibility of performing photon-number-resolving (PNR) detection to isolate the constituent quantum multiphoton wave packets of a classical light field. We experimentally verified the coherence properties of isolated vacuum systems and wave packets with up to 16 photons. Our findings not only demonstrate the possibility of observing quantum properties of classical macroscopic objects but also establish a fundamental bridge between the classical and quantum worlds.

Learning quantum phases via single-qubit disentanglement

Identifying phases of matter presents considerable challenges, particularly within the domain of quantum theory, where the complexity of ground states appears to increase exponentially with system size. Quantum many-body systems exhibit an array of complex entanglement structures spanning distinct phases. Although extensive research has explored the relationship between quantum phase transitions and quantum entanglement, establishing a direct, pragmatic connection between them remains a critical challenge. In this work, we present a novel and efficient quantum phase transition classifier, utilizing disentanglement with reinforcement learning-optimized variational quantum circuits. We demonstrate the effectiveness of this method on quantum phase transitions in the transverse field Ising model (TFIM) and the XXZ model. Moreover, we observe the algorithm's ability to learn the Kramers-Wannier duality pertaining to entanglement structures in the TFIM. Our approach not only identifies phase transitions based on the performance of the disentangling circuits but also exhibits impressive scalability, facilitating its application in larger and more complex quantum systems. This study sheds light on the characterization of quantum phases through the entanglement structures inherent in quantum many-body systems.

Interpretation of quantum theory in a cosmological perspective

We reconsider the problem of the interpretation of the quantum theory (QT) in the perspective of the entire universe and of the Bohr's idea that the classical language is the language of our experience and QT acquires a meaning only with a reference to it. We distinguish a classical or macroscopic state, and a quantum or microscopic one that is perceived only through the modifications that it induces in the first. The macroscopic state is specified by a set of variables, a classical energy–momentum tensor and conserved currents, which are supposed to have always a well-defined value. The microscopic state and dynamics are expressed by the usual QT formalism. For the macroscopic variables, a basic distribution of probability is postulated in terms of quantum operators and a statistical operator, what replace the usual probability rule of QT. For the universe, a variance of the ΛCDM model with Ω=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega = 1$$\\end{document} is assumed, one inflaton, a Goldstone type potential, initial time at t=-∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t = - \\infty$$\\end{document}, expectation values of all fundamental fields vanishing for t→-∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t \ o - \\infty$$\\end{document}. The scalar fluctuations in the cosmic microwave background is correctly explained, but the absence of the tensor fluctuations remains not understood. This seems to suggest that gravity is a pure classical phenomenon what perhaps could be accommodated in our framework.

Deciphering the adsorption and sensing performance of Al24N24 and B24N24 nanoclusters as a drug delivery system for nitrosourea anticancer drug: A DFT insight

Nanomaterials for drug detection are crucial in pharmaceutical research, especially in cancer therapy applications like nitrosourea. The purpose of this work was to examine the sensitivity of Al24N24 and B24N24 nanocages for the detection of nitrosourea by using density functional theory (DFT). Different analyses were performed such as adsorption energy (Eads) studies, frontier molecular orbitals (FMOs), natural bond orbitals (NBO), global indices of reactivity, UV-Vis studies, molecular electrostatic potential (MEP), non-covalent interaction (NCI), quantum theory of atoms in molecules (QTAIM) and sensor mechanism. The adsorption of nitrosourea on Al24N24 shows the highest values of adsorption energies with the value of −59.239, −55.986, and −51.019 kcal/mol for O/6m-AN, plan/6m-AN, and plan/8m-AN respectively. On the other hand, B24N24 complexes show fewer adsorption energies with the notable presence in plan/6m-BN, O/4m-BN, and plan/8m-BN that have the values of −11.064, −10.983, and −10.064 kcal/mol respectively. The energy gap of Al24N24 and B24N24 complexes decrease from 4.120 eV and 6.493 eV respectively for bare nanocage showing the potential of using these cages for nitrosourea (NUr) detection. FMOs studies reveal that among all designed complexes the lowest energy gap is present in O/4m-AN having a value of 2.913 eV. Moreover, global indices of reactivity suggest the increase in softness for Al24N24 complexes from 0.2427 eV for bare nanocage to 0.3433 eV for O/4m-AN. Similarly, the softness for B24N24 complexes also increases from 0.1540 eV for bare cage to 0.3012 eV for O/B-BN. Sensitivities for NUr in O/B-BN, O/4m-BN, plan/6m-BN and plan/8m-BN are 0.896, 0.870, 0.834 and 0.815 respectively. Moreover, the recovery time of NUr drug from BN nanocage is also very short as 7.53 × 10-12 s for O/N-BN. Topological analysis predict the non-covalent nature of interaction present between AN and BN nanocages. The electrical conductivity values are increased after the adsorption process. The highest electrical conductivity is present in AN complexes such as 4.41 × 1012 S/m for O/4m-AN due to low energy gap of 2.91 eV. The sensor mechanism reflects the high values of sensitivity for B24N24 complexes due to narrow energy gaps. Thus, B24N24 could be a fine candidate for the detection of nitrosourea and as a drug delivery vehicle for nitrosourea to treat cancer.

Exploration of Free Energy Surface of the Au10 Nanocluster at Finite Temperature.

The first step in comprehending the properties of Au10 clusters is understanding the lowest energy structure at low and high temperatures. Functional materials operate at finite temperatures; however, energy computations employing density functional theory (DFT) methodology are typically carried out at zero temperature, leaving many properties unexplored. This study explored the potential and free energy surface of the neutral Au10 nanocluster at a finite temperature, employing a genetic algorithm coupled with DFT and nanothermodynamics. Furthermore, we computed the thermal population and infrared Boltzmann spectrum at a finite temperature and compared it with the validated experimental data. Moreover, we performed the chemical bonding analysis using the quantum theory of atoms in molecules (QTAIM) approach and the adaptive natural density partitioning method (AdNDP) to shed light on the bonding of Au atoms in the low-energy structures. In the calculations, we take into consideration the relativistic effects through the zero-order regular approximation (ZORA), the dispersion through Grimme's dispersion with Becke-Johnson damping (D3BJ), and we employed nanothermodynamics to consider temperature contributions. Small Au clusters prefer the planar shape, and the transition from 2D to 3D could take place at atomic clusters consisting of ten atoms, which could be affected by temperature, relativistic effects, and dispersion. We analyzed the energetic ordering of structures calculated using DFT with ZORA and single-point energy calculation employing the DLPNO-CCSD(T) methodology. Our findings indicate that the planar lowest energy structure computed with DFT is not the lowest energy structure computed at the DLPN0-CCSD(T) level of theory. The computed thermal population indicates that the 2D elongated hexagon configuration strongly dominates at a temperature range of 50-800 K. Based on the thermal population, at a temperature of 100 K, the computed IR Boltzmann spectrum agrees with the experimental IR spectrum. The chemical bonding analysis on the lowest energy structure indicates that the cluster bond is due only to the electrons of the 6 s orbital, and the Au d orbitals do not participate in the bonding of this system.

Characterising transformations between quantum objects, 'completeness' of quantum properties, and transformations without a fixed causal order

Many fundamental and key objects in quantum mechanics are linear mappings between particular affine/linear spaces. This structure includes basic quantum elements such as states, measurements, channels, instruments, non-signalling channels and channels with memory, and also higher-order operations such as superchannels, quantum combs, n-time processes, testers, and process matrices which may not respect a definite causal order. Deducing and characterising their structural properties in terms of linear and semidefinite constraints is not only of foundational relevance, but plays an important role in enabling the numerical optimisation over sets of quantum objects and allowing simpler connections between different concepts and objects. Here, we provide a general framework to deduce these properties in a direct and easy to use way. While primarily guided by practical quantum mechanical considerations, we also extend our analysis to mappings between general linear/affine spaces and derive their properties, opening the possibility for analysing sets which are not explicitly forbidden by quantum theory, but are still not much explored. Together, these results yield versatile and readily applicable tools for all tasks that require the characterisation of linear transformations, in quantum mechanics and beyond. As an application of our methods, we discuss how the existence of indefinite causality naturally emerges in higher-order quantum transformations and provide a simple strategy for the characterisation of mappings that have to preserve properties in a 'complete' sense, i.e., when acting non-trivially only on parts of an input space.

QM/CG-MM: Systematic Embedding of Quantum Mechanical Systems in a Coarse-Grained Environment with Accurate Electrostatics.

Quantum Mechanics/Molecular Mechanics (QM/MM) can describe chemical reactions in molecular dynamics (MD) simulations at a much lower cost than ab initio MD. Still, it is prohibitively expensive for many systems of interest because such systems usually require long simulations for sufficient statistical sampling. Additional MM degrees of freedom are often slow and numerous but secondary in interest. Coarse-graining (CG) is well-known to be able to speed up sampling through both reduction in simulation cost and the ability to accelerate the dynamics. Therefore, embedding a QM system in a CG environment can be a promising way of expediting sampling without compromising the information about the QM subsystem. Sinitskiy and Voth first proposed the theory of Quantum Mechanics/Coarse-grained Molecular Mechanics (QM/CG-MM) with a bottom-up CG mapping. Mironenko and Voth subsequently introduced the DFT-QM/CG-MM formalism to couple a Density Functional Theory (DFT) treated QM system and to an apolar environment. Here, we present a more complete theory that addresses MM environments with significant polarity by explicitly accounting for the electrostatic coupling. We demonstrate our QM/CG-MM method with a chloride-methyl chloride SN2 reaction system in acetone, which is sensitive to solvent polarity. The method accurately recapitulates the potential of mean force for the substitution reaction, and the reaction barrier from the best model agrees with the atomistic simulations within sampling error. These models also have generalizability. In two other reactive systems that they have not been trained on, the QM/CG-MM model still achieves the same level of agreement with the atomistic QM/MM models. Finally, we show that in these examples the speed-up in the sampling is proportional to the acceleration of the rotational dynamics of the solvent in the CG system.

Quantum Theory of Lee–Naughton–Lebed’s Angular Effect in Strong Electric Fields

Quantum Theory of Lee–Naughton–Lebed’s Angular Effect in Strong Electric Fields