Search results for "Equilibrium"
showing 10 items of 1021 documents
Dynamic Self-Consistent Field Approach for Studying Kinetic Processes in Multiblock Copolymer Melts
2020
The self-consistent field theory is a popular and highly successful theoretical framework for studying equilibrium (co)polymer systems at the mesoscopic level. Dynamic density functionals allow one to use this framework for studying dynamical processes in the diffusive, non-inertial regime. The central quantity in these approaches is the mobility function, which describes the effect of chain connectivity on the nonlocal response of monomers to thermodynamic driving fields. In a recent study [Mantha et al, Macromolecules 53, 3409 (2020)], we have developed a method to systematically construct mobility functions from reference fine-grained simulations. Here we focus on melts of linear chains …
Modeling of biomolecular machines in non-equilibrium steady states
2021
Numerical computations have become a pillar of all modern quantitative sciences. Any computation involves modeling--even if often this step is not made explicit--and any model has to neglect details while still being physically accurate. Equilibrium statistical mechanics guides both the development of models and numerical methods for dynamics obeying detailed balance. For systems driven away from thermal equilibrium such a universal theoretical framework is missing. For a restricted class of driven systems governed by Markov dynamics and local detailed balance, stochastic thermodynamics has evolved to fill this gap and to provide fundamental constraints and guiding principles. The next step…
Giant Mechanocaloric Effects in Fluorite-Structured Superionic Materials
2016
Mechanocaloric materials experience a change in temperature when a mechanical stress is applied on them adiabatically. Thus, far, only ferroelectrics and superelastic metallic alloys have been considered as potential mechanocaloric compounds to be exploited in solid-state cooling applications. Here we show that giant mechanocaloric effects occur in hitherto overlooked fast ion conductors (FIC), a class of multicomponent materials in which above a critical temperature, Ts, a constituent ionic species undergoes a sudden increase in mobility. Using first-principles and molecular dynamics simulations, we found that the superionic transition in fluorite-structured FIC, which is characterized by …
The yellow toxins produced by Cercospora Beticola. Part VIII : Chemical equilibrium between beticolins ; structures of minor compounds : beticolin 6 …
1994
Abstract a general chemical transformation of the “linear” beticolin skeleton (beticolin 2 and 4) into a “bent” beticolin skeleton (cebetin A and beticolin 3 respectively) is described. Beticolins 6 and 8, minor components of mycelial extract are also characterized as minor compounds resulting from these transformations.
Analytic second derivatives for the spin-free exact two-component theory
2011
The formulation and implementation of the spin-free (SF) exact two-component (X2c) theory at the one-electron level (SFX2c-1e) is extended in the present work to the analytic evaluation of second derivatives of the energy. In the X2c-1e scheme, the four-component one-electron Dirac Hamiltonian is block diagonalized in its matrix representation and the resulting "electrons-only" two-component Hamiltonian is then used together with untransformed two-electron interactions. The derivatives of the two-component Hamiltonian can thus be obtained by means of simple manipulations of the parent four-component Hamiltonian integrals and derivative integrals. The SF version of X2c-1e can furthermore exp…
A theoretical and experimental study of the formation mechanism of 4-X-chalcones by the Claisen–Schmidt reaction
2000
Abstract A theoretical and experimental study on the formation of 4-X-chalcones (X=H, Cl, F, OCH3, N(CH3)2) was carried out by the Claisen–Schmidt reaction. The influence of pH and temperature was analyzed. Under the adopted experimental conditions 4-X-chalcones were the only reaction products. In the theoretical study, the thermodynamic magnitudes and the reactivity indexes calculated with the AM1 method were used. The mechanism of Nayak and Rout was analyzed critically and a new mechanism was proposed, characterized by: (1) rapid nucleophilic attack of the catalyst (OH−) on the carbon atom of the methyl group of acetophenone; (2) attacks of the acetophenonate ion on the carbon atom of the…
Transport coefficients of n-butane into and through the surface of silicalite-1 from non-equilibrium molecular dynamics study
2009
We have studied coupled heat and mass transfer of n-butane through a membrane of silicalite-1. A description of the surface was given using non-equilibrium thermodynamics, and transport coefficients were determined. Three independent coefficients were found for the whole surface: the resistance to heat transfer, the coupling coefficient and the resistance to mass transfer. These coefficients were defined in stationary state. All resistances are significant, and show that the surface acts as a barrier to transport. A new scheme was devised to find the enthalpy of adsorption, from two particular coupling coefficients, namely the measurable heats of transfer. The method yields the enthalpy of …
Activity mediated phase separation: Can we understand phase behavior of the nonequilibrium problem from an equilibrium approach?
2016
We present results for structure and dynamics of mixtures of active and passive particles, from molecular dynamics (MD) simulations and integral equation theory (IET) calculations, for a physically motivated model. The perfectly passive limit of the model corresponds to the phase-separating Asakura-Oosawa model for colloid-polymer mixtures in which, for the present study, the colloids are made self-propelling by introducing activity in accordance with the well known Vicsek model. Such activity facilitates phase separation further, as confirmed by our MD simulations and IET calculations. Depending upon the composition of active and passive particles, the diffusive motion of the active specie…
Aqueous Solubility Diagrams for Cementitious Waste Stabilization Systems: II, End-Member Stoichiometries of Ideal Calcium Silicate Hydrate Solid Solu…
2001
Solubility in the fully hydrated CaO–SiO2–H2O system can be best described using two ideal C-S-H-(I) and C-S-H-(II) binary solid solution phases. The most recent structural ideas about the C-S-H gel permit one to write stoichiometries of polymerized C-S-H-(II) end-members as hydrated precursors of the stable tobermorite and jennite minerals in the form of 5Ca(OH)2·6SiO2·5H2O and 10Ca(OH)2·6SiO2·6H2O, respectively. For thermodynamic modeling purposes, it is more convenient to express the number of basic silica and portlandite units in these stoichiometries using the coefficients nSi and nCa. Thermodynamic solid-solution aqueous-solution equilibrium modeling by applying the Gibbs energy minim…
Static and dynamic screening effects in the electrostatic self-assembly of nano-particles.
2014
In the description of charge screening in the electrostatic self-assembly of nanoparticles (molecules) embedded into a polar solvent, the static screening effects (a contribution associated with the rapid spatial redistribution of small and highly mobile ions of a solvent) are traditionally treated phenomenologically, using the Yukawa short-range potential for describing the interaction between these particles. However, this model has a limited range of applicability being valid only for infinitely diluted systems and high salt concentrations. During a slow self-assembling process with nanoparticle formation, very dense structural elements (aggregates) are formed, in which the distances bet…