Research

Current projects

Properties of water and seawater in metastable states. Experiment, molecular simulation, and thermodynamic modeling.

Principal researchers: J. Hruby; Inst. of Thermomechanics, Acad. Sci.
and
I. Nezbeda; J. E. Purkinje Univ.
[Supported by the Czech Science Foundations (2016-2018)]
(back-to-list-of-projects)
SUMMARY
The data situation for thermodynamic properties of metastable supercooled pure water and seawater is unsatisfactory for the validation of the present standards such as IAPWS-95 and development of future models. Moreover, the region is interesting due to the vicinity of the hypothesized second critical point. Data for metastable supersaturated steam is nonexistent despite its importance for power generation. We propose performing accurate measurements of the expansivity and compressibility of supercooled water and seawater up to 200 MPa using recently developed unique apparatus, which will be further improved. Properties of supercooled water, seawater and supersaturated steam will also be computed by molecular simulations using polarizable intermolecular potentials and advanced methods for ionic interactions. Experimental and simulated data will be represented by models based on statistical

Thermodynamics of polymer solutions: experiments meet theory and vice versa

Principal researcher: I. Wichterle
Inst. Chem. Process Fund., Acad. Sci.
[Supported by the Czech Science Foundations (2015-2017)]
(back-to-list-of-projects)
SUMMARY
The project aims at
(1) obtaining accurate vapour-liquid equilibrium data for industrially important systems containing polymer (mostly biodegradable) + solvent,
(2) obtaining results on the conformal behaviour of polymers in solutions at the given thermodynamic conditions and their impact on the phase equilibria,
(3) developing a truly molecular-based computer-aided theory as an alternative to empirical and semi-empirical models as e.g., SAFT.
The experimental part will focus on improving methodology of getting accurate data on phase equilibria over a wide range of thermodynamic conditions. New simple short-range models will be developed to be used in a perturbation expansion for the Helmholtz free energy. Correctness and accuracy of the theory will be verified by molecular simulations and experimental data. The results acquired can be immediately applied in the design of efficient separation units in chemical and petroleum industry.

Modeling of complex molecular fluids at extreme conditions: Theory and applications

Principal researchers: I. Nezbeda; J. E. Purkinje Univ.
and
A. Trokhymchuk, Inst. Condensed Matter Phys., Ukrainian Acad. Sci.
[Bilateral project supported by the Czech Acad. Sci. and Ukrainian Acad. Sci. (2016-2018)]
(back-to-list-of-projects)
SUMMARY
The project aims at studying complex molecular fluids at extereme conditions (high temperatures and pressures) encountered in various technological processes, and developing a molecular-level understanding of their properties and theory. It represents a continuation of our collaboration which started in 2008-2010 and during 2011-2013 it resulted in 4 joint papers already published in international journals and 2 more papers are under preparation and will be submitted. The proposed studies are based on a new general approach we have developed recently for deriving an equation of state of fluids in an analytic form and which we have already verified for a simple fluid models. Its implementation for actual systems consists of several steps which may vary for different classes of fluids such as ionic and hydrogen bonding fluids and whose solution is the goal of the proposed project. Specifically, an accurate definition and treatment of the reference system, incorporation into a reference system strongly orientation-dependent interactions (e.g., water) and extension to mixtures. The collaboration between the two groups combines expertise in their respective fields:: analytic theories of associating and Coulombic systems (Lviv group) and molecular simulations (Prague group).

Recently accomplished projects

Polymer solutions in an external field: Molecular understanding of electrospinning

Principal researchers: I. Nezbeda, J. E. Purkinje Univ.
and
D. Lukas, Technical Univ. Liberec

[Supported by the Czech Science Foundation (2012-2015)]
(back-to-list-of-projects)
SUMMARY
The project studies polymer solutions subject to an external electric field with respect to the technology of electrospinning from the free surface. Using molecular modeling and molecular simulations complemented by experiment, an attempt is made to reveal relations between various molecular and/or thermodynamic properties affecting the process of electrospinning. Particularly, given a speci c polymer and solvent, the relations between the conformational behavior of the polymer, concentration and composition of the solvent and strength of the electric field with the surface tension and diffusivity. These results will then provide the input information into semiempirical and theoretical macroscopic methods. The conclusions and recommendations are veri ed by comparison with experimental data obtained also within this project.

Simple and complex models of aqueous solutions: The effect of nonadditive interactions

Principal researcher: I. Nezbeda, Inst. Chem. Process Fund., Acad. Sci.
[Supported by the Grant Agency of the Academy of Sciences (2008-2012)]
(back-to-list-of-projects)
SUMMARY
Aqueous solutions of lower alcohols and typical volatile organic compounds, represented by nonadditive pseudo hard bodies and realistic both nonpolarizable and polarizable models, will be studied by computer simulations at both simple and complex levels. The simple models serve as a basis for development of a (perturbation) theory of these fluids and their mixtures. The simulations of the complex models will investigate the role of nonadditive interactions, implemented by polarizability and/or modified cross interactions. The emphasis on nonadditive models and corresponding theory is dictated by the failure of standard, additive approaches to reliably describe the experimental data over the entire concentration range. The development of methodology of computer simulations, which is an integral part of this project, includes efficient methods for simulations of polarizable fluids and their generalization for determination of phase equilibria.

Nonadditive interactions in aqueous solutions of electrolytes: Role of polarizability and cross interactions

Principal researchers: I. Nezbeda, J. E. Purkinje Univ. and
A. A. Chialvo, Oak Ridge Natl. Lab., Oak Ridge, TN, USA
[Bilateral project supported by the Ministry of Education, Czech Rep., and (2007-2011)]
(back-to-list-of-projects)
SUMMARY
The ultimate goal of the project is to develop accurate transferable force fields for simple (mono-, di-, and tri-valent) ions consistent with the polarizable GCP model of water for the description of both bulk and interfacial aqueous systems over a wide range of compositions and thermodynamic states.
Last update: February 1, 2016