Transport properties functional representation

Equilibrium time correlation function expressions for transport properties can be derived using linear response theory [3]. Linear response theory can be carried out directly on the Wigner transformed equations of motion to obtain the transport properties as correlation functions involving Wigner transformed quantities. Alternatively, we may carry out the linear response analysis in terms of abstract operators and insert the Wigner representation of operators in the final form for the correlation function. We use the latter route here. 

Basic requirements on feasible systems and approaches for computational modeling of fuel cell materials are (i) the computational approach must be consistent with fundamental physical principles, that is, it must obey the laws of thermodynamics, statistical mechanics, electrodynamics, classical mechanics, and quantum mechanics (ii) the structural model must provide a sufficiently detailed representation of the real system it must include the appropriate set of species and represent the composition of interest, specified in terms of mass or volume fractions of components (iii) asymptotic limits, corresponding to uniform and pure phases of system components, as well as basic thermodynamic and kinetic properties must be reproduced, for example, density, viscosity, dielectric properties, self-diffusion coefficients, and correlation functions (iv) the simulation must be able to treat systems of sufficient size and simulation time in order to provide meaningful results for properties of interest and (v) the main results of a simulation must be consistent with experimental findings on structure and transport properties. 

Functional representation of data sets A general representation of any transport property correlation can be written as... 

The Subcommittee on Transport Properties has discharged its responsibilities through the work of groups of research workers active in the field drawn from all over the world. These groups have collaborated in the preparation of representations of the viscosity, thermal conductivity and diffusion coefficients of pure fluids and their mixtures over wide ranges of thermodynamic states. The rqrresentations have alnK>st always been based upon an extensive body of expaimental data for the property in question accumulated over many years by the efforts of laboratories worldwide. The results of this work have been published under the auspices of the subconunittee, with international endorsement, in Journal of Physical and Chemical Reference Data and International Journal of Thermophysics. The series of papers produced provides equations that describe the properties as a function of temperature and density that can be readily coded to yield transport properties at any prescribed thermodynamic state with a defined uncertainty. 

The proper representation of the thermodynamic properties of out-of-equilibrium systems such as glassy polymers is still an open question. Reliable correlations and predictive expressions for the mass transport properties in polymeric glasses as a function of temperature and concentration are also lacking. 

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