arXiv subjects

Irina Smirnova

Publications and source records attributed to Irina Smirnova.

15 recordsLinked to original sources

arXiv2026

Extension of openCOSMO-RS Into a Full Open-Source Equation of State: Implementation, Parameterization, and Benchmarking

The COSMO-SAC-Phi model developed by Soares et al. extends the COSMO-SAC activity-coefficient framework into a full equation of state by explicitly accounting for pressure effects. In this approach, pure substances and mixtures are represented as pseudo-mixtures consisting of the actual number of moles and an additional pseudo-component that describes free volume, or holes. In this work, we implement this extension within the openCOSMO-RS framework and evaluate it using a large and diverse set of molecules and binary systems. The resulting equation of state includes an extensive open-source parameter set with around 1800 pure-component entries, made freely available to the academic community. The four pure-component parameters were fitted to vapor-pressure and liquid-molar volume data for each substance. Model performance was assessed against two benchmark equation-of-state databases, one for pure compounds and one for binary mixtures, without introducing any binary interaction parameters. The resulting openCOSMO-RS-Phi model reproduces the accuracy of the original COSMO-SAC-Phi formulation while providing a fully open-source and accessible implementation for the scientific community. Beyond its immediate utility, it also establishes a foundation for future development of predictive EoS for electrolyte solutions.

physics.chem-ph↗

arXiv2025

Enhancing Swelling Kinetics of pNIPAM Lyogels: The Role of Crosslinking, Copolymerization, and Solvent

Stimuli-responsive lyogels are known for their ability to undergo significant macroscopic changes when exposed to external stimuli. While thermo-responsive gels, such as poly N isopropylacrylamide (pNIPAM), have been extensively studied across various applications, solvent-induced swelling has predominantly been investigated in aqueous solutions. This study explores the tailoring of lyogel formulations for future applications by controlling their solvent-induced swelling behavior, comparing both homopolymeric and semi-interpenetrating polymer networks (semi-IPNs). In contrast to most previous studies, the impact of chemical and physical crosslinking, as well as copolymer inclusion, on the swelling behavior and mechanical properties of lyogels in organic solvents is examined and compared with solvent-induced swelling kinetics measurements. The results demonstrate that increasing chemically crosslinking in homopolymers and physically crosslinking in semi-IPNs enhances mechanical stability, while improving mass transport properties and solvent exchange kinetics. However, increases degree of crosslinking results in a prolonged response time to the solvent exchange stimulus and a reduction in the overall swelling capacity of the lyogels. Furthermore, variations in solvent properties, including molecular size and diffusion rates, significantly influence the swelling kinetics, whereas smaller, faster-diffusing solvents leading to more pronounced solvent spillage effects. Our findings highlight the complex interplay between gel formulation, network structure, and solvent nature in determining the solvent-induced swelling kinetics of lyogels, providing insights into how these materials can be tailored for specific applications especially those requiring short response times and optimized mechanical properties.

cond-mat.soft↗

arXiv2025

A comprehensive approach to incorporating intermolecular dispersion into the openCOSMO-RS model. Part 2: Atomic polarizabilities

openCOSMO-RS is an open-source predictive thermodynamic model that can be applied to a broad range of systems in various chemical and biochemical engineering domains. This study focuses on improving openCOSMO-RS by introducing a new dispersion term based on atomic polarizabilities. We evaluate different methods for processing polarizability data, including scaling and combining it to compute segment-segment dispersion interaction energies, with a focus on halocarbon systems. The results demonstrate that the modified model outperforms our previous method developed in the first part of this work (Grigorash et al., 2024) , while at the same time requiring fewer adjustable parameters. The approach was applied to a broad dataset of over 50,000 data points, consistently increasing the accuracy across a variety of data types. These findings suggest that atomic polarizability is a valuable descriptor for refining dispersion interactions in predictive thermodynamic models.

cond-mat.soft↗

arXiv2024

Mixed Fourier norm spaces of analytic functions on the upper half-plane and Toeplitz operators

We introduce and study weighted spaces of functions with mixed norm on the upper half-plane, defined in terms of Fourier transform. We give a characterization of analytic functions within these spaces, and in particular, we provide an analog of the Paley-Wiener theorem in this setting. As an application, we consider Toeplitz operators with vertical symbols in these new spaces.

math.FA↗

arXiv2024

Exploring pNIPAM Lyogels: Experimental Study on Swelling Equilibria in Various Organic Solvents and Mixtures, Supported by COSMO-RS Analysis

Stimuli-responsive lyogels are considered to be smart materials due to their capability of undergoing significant macroscopic changes in response to external triggers. Due to their versatile and unique properties, smart lyogels exhibit great potential in various applications such as drug delivery or actuation processes. While Poly-N-isopropylacrylamide (pNIPAM) is widely known as a thermo-responsive material, it also shows significant solvent-responsive swelling behavior. As polar solvents induce strong swelling due to hydrogen bonding with the amide group, nonpolar solvents lead to significant shrinkage of the lyogels. The aim of this study is to investigate and to model this behavior for future application in chemical or biochemical reactors. As a current area of research, incorporating smart hydrogel technology into (bio-)chemical reactors facilitates the development of smart reactor systems. Applying thermodynamic modelling with the gE model COSMO-RS on the monomer or oligomers of pNIPAM, the correlation between solvent-polymer interactions and the degree of swelling can be observed. pNIPAM derivatives exhibit low infinitive dilution activity coefficients (IDACs) in polar solvents with large degrees of swelling, while displaying an increase of IDACs in nonpolar solvents. Hydrogen bonds dominate the swelling behavior of lyogels not only in pure solvents but also in mixtures of solvents with varying polarity. Even in mixtures containing high amounts of nonpolar solvents, large degrees of swelling were observed due to the uptake of the polar solvent in the lyogel matrix. This effect can be observed in binary solvent mixtures but also in representative mixtures along an esterification reaction with varying carboxylic chain length of alcohol and carboxylic acids.

cond-mat.soft↗

arXiv2024

Predicting solvation free energies for neutral molecules in any solvent with openCOSMO-RS

The accurate prediction of solvation free energies is critical for understanding various phenomena in the liquid phase, including reaction rates, equilibrium constants, activity coefficients, and partition coefficients. Despite extensive research, precise prediction of solvation free energies remains challenging. In this study, we introduce openCOSMO-RS 24a, an improved version of the open-source COSMO-RS model, capable of predicting solvation free energies alongside other liquid-phase properties. We parameterize openCOSMO-RS 24a using quantum chemical calculations from ORCA 6.0, leveraging a comprehensive dataset that includes solvation free energies, partition coefficients, and infinite dilution activity coefficients for various solutes and solvents at 25 {\deg}C. Additionally, we develop a Quantitative Structure-Property Relationships model to predict molar volumes of the solvents, an essential requirement for predicting solvation free energies from structure alone. Our results show that openCOSMO-RS 24a achieves an average absolute deviation of 0.45 kcal/mol for solvation free energies, 0.76 for partition coefficients, and 0.51 for infinite dilution activity coefficients, demonstrating improvements over the previous openCOSMO-RS 22 parameterization and comparable results to COSMOtherm 24 TZVP. A new command line interface for openCOSMO-RS 24a was developed which allows easy acces to the solvation energy model directly from within ORCA 6.0. This represents a significant advancement in the predictive modeling of solvation free energies and other solution-phase properties, providing researchers with a robust tool for applications in chemical and materials science.

physics.chem-ph↗

arXiv2024

A comprehensive approach to incorporating intermolecular dispersion into the openCOSMO-RS model. Part 1: Halocarbons

The COSMO-RS (Conductor-like Screening Model for Real Solvents) is a predictive thermodynamic model that has found diverse applications in various domains like chemical engineering, environmental chemistry, nanotechnology, material science, and biotechnology. Its core concept involves calculating the screening charge density on the surface of each molecule and letting these surface patches interact with each other to calculate thermodynamic properties. In this study, we aim to enhance the performance of the open-source implementation openCOSMO-RS by incorporating dispersive interactions between the paired segments. Several parametrizations were systematically evaluated through the extensive regression analysis using a comprehensive database of Vapor-Liquid Equilibrium (VLE), Liquid-Liquid Equilibrium (LLE) and Infinite Dilution Activity Coefficients (IDACs). Furthermore, the influence of different combinatorial terms on the model performance was investigated. Our findings indicate that incorporating dispersive interactions significantly improves the accuracy of phase equilibrium predictions for halocarbons and refrigerant mixtures.

cond-mat.soft↗

arXiv2024

Thermodynamic modeling using Extended UNIQUAC and COSMO-RS-ES models: Case study of the cesium nitrate - water system over a large range of temperatures

A comparison of two thermodynamic models is presented using the water-cesium nitrate system as case study. Both models were able to model the thermodynamic properties such as the osmotic coefficient, vapor pressure, mean activity coefficient and solubility with good accuracy. We show that it is possible to reproduce the temperature dependency of the properties using a simple set of parameters in the case of Extended UNIQUAC. Furthermore, COSMO-RS-ES is a completely predictive model adjusted to data at 298.15 K, which is applied for the first time to other temperatures.

cond-mat.soft↗

arXiv2023

Confidence Interval and Uncertainty Propagation Analysis of SAFT-type Equations of State

Thermodynamic models and, in particular, SAFT-type equations are vital in characterizing complex systems. This paper presents a framework for sampling parameter distributions in PC-SAFT and SAFT-VR Mie equations of state to understand parameter confidence intervals and correlations. We identify conserved quantities contributing to significant correlations. Comparing the equations of state, we find that additional parameters introduced in the SAFT-VR Mie equation increase relative uncertainties (1\%-2\% to 3\%-4\%) and introduce more correlations. When incorporating association through additional parameters, relative uncertainties increase, but correlations slightly decrease. We investigate how uncertainties propagate to derived properties and observe small uncertainties for that data with which the parameters were regressed, especially for saturated-liquid volumes. However, extrapolating to saturated-vapour volumes yields larger uncertainties due to the larger isothermal compressibility. Near the critical point, uncertainties in saturated volumes diverge due to increased sensitivity of the isothermal compressibility to parameter uncertainties. This effect significantly impacts bulk properties, particularly isobaric heat capacity, where uncertainties near the critical point become extremely large, even when these uncertainties are small. We emphasize that even small uncertainties near the critical point lead to divergences in predicted properties.

physics.chem-ph↗

arXiv2023

Evaluation and Refinement of the novel predictive electrolyte model COSMO-RS-ES based on solid-liquid equilibria of salts and Gibbs free Energies of Transfer of Ions

The new predictive electrolyte model COSMO-RS-ES is evaluated and refined for the calculation of solubilities of salts in mixed solvent systems. It is demonstrated that the model is capable of predicting solid-liquid equilibria at 25 °C for ammonium and alkali metal salts quite accurately in a wide variety of solvent mixtures. Furthermore, through the introduction of Gibbs free energies of transfer of single ions it is shown that the model performance can be improved even further. This new data type also allows for an ion-specific way of evaluating the model for the first time. For some systems when calculating the solubility, larger deviations are observed, but for the vast majority of systems the model delivers good predictions. This shows that COSMO-RS-ES is a valuable tool for calculation of phase equilibria in electrolyte systems especially when the scarcity of data impede the application of models that require a higher number of parameters.

cond-mat.stat-mech↗

arXiv2023

Calculation of Thermodynamic Equilibria with the Predictive Electrolyte Model COSMO-RS-ES: Improvements for Low Permittivity Systems

The predictive electrolyte model COSMO-RS-ES is refined to improve the description of systems at 25°C in which strong ion pairing is expected due to a low static permittivity of the liquid phase. Furthermore, the short-range ion energy interaction equations have been modified to better describe the misfit and energy interaction terms between ions and solvent molecules. In addition, the salt solubility database is extended with additional non-aqueous systems containing solvents that have a low (ε_s<15) dielectric constant and promote near to full ion association. Throughout this work it is demonstrated that liquid-liquid equilibrium calculations and solid-liquid equilibrium predictions for electrolyte systems can be markedly improved with the inclusion of Bjerrum treatment based phenomenological considerations while introducing only one general additional parameter. Our modified approach reinforces the capabilities of COSMO-RS ES as a powerful predictive tool for the calculation of phase equilibria in systems with scarce experimental data.

physics.chem-ph↗

arXiv2023

Impact of extended long-range electrostatics on the correlation of liquid-liquid equilibria in aqueous ionic liquid systems

Recently an improved long-range model for electrolyte solutions was developed that is applicable from infinite dilution to pure salt. This paper tests this claim for the first time applying it to the calculation of liquid-liquid equilibria for mixtures of different ionic liquids (ILs) and water. The conventional Pitzer-Debye-Hückel (PDH) equation is compared to two of its new, thermodynamically consistent extensions. Both development stages, the extended PDH term and the modified-extended PDH, account for concentration dependent mixture properties instead of using solvent properties. The latter one additionally introduces a modified parameter of closest approach which improves the overall performance of the model for high electrolyte concentrations in systems with variable or low permittivities. To account for the short-range interactions, these long-range models are coupled with the UNIversal QUAsi-Chemical (UNIQUAC) model. Three modeling strategies were tested for the short-range contribution. First, the UNIQUAC parameters were adjusted to each system individually, then the binary interaction parameters were the same for each binary interaction type for all the systems and lastly a linear function of the carbon number was used where possible. For all systems and all modeling strategies tested, the predictive performance increased from PDH to E-PDH and then to ME-PDH. Overall, an introduction of concentration dependent properties and the modification added to ME-PDH enhanced modeling performance when describing these systems, showing the general applicability of this novel long-range term.

cond-mat.soft↗

arXiv2023

On the analogy between the restricted primitive model and capacitor circuits: Semi-empirical alternatives for over- and underscreening in the calculation of mean ionic activity coefficients

The analogy between the restricted primitive model and capacitor circuits, originally described decades ago for the Mean Spherical Approximation, is explored to demonstrate its transferability in linearized electrolyte theories. On this basis, we offer an explanation of why treating the salt diameter as a free adjustable parameter blurs differences between electrolyte theories in the calculation of mean ionic activity coefficients. Furthermore, a capacitor circuit analogy with an approximation of the Dressed Ion Theory is applied to develop a modified closest approach parameter "b" for the Pitzer-Debye-Hückel term. This modification is able to account for the qualitative effects of over- and underscreening in the calculation of mean ionic activity coefficients. This is achieved by defining "b" as a semi-empirical function that allows close resemblance with the multiple decay-length extension of the Debye-Hückel theory for high dielectric constant values and that lies close to recommended literature values of "b" for low dielectric constant values. Finally, as proof of principle, this modified semi-empirical Pitzer-Debye-Hückel term is implemented in the predictive COSMO-RS-ES model, an own reimplementation of the COSMO-RS theory developed for thermodynamic property calculations of electrolyte systems. It is shown that the modified semi-empirical Pitzer-Debye-Hückel term is an effective replacement for the recently published version of COSMO-RS-ES with explicit considerations for ion pairing. This reduces the modelling complexity by implicitly considering ion pairing and improves overall qualitative performance for the prediction of salt solubilities in mixed-solvent systems and even mean ionic activity coefficients in non-aqueous media.

physics.chem-ph↗

arXiv2023

On the analogy between the restricted primitive model and capacitor circuits. Part II: A generalized Gibbs-Duhem consistent extension of the Pitzer-Debye-Hückel term with corrections for low and variable relative permittivity

We present a novel, thermodynamically consistent modification of the Pitzer-Debye-Hückel term and its extension for concentration dependent density, molar mass and relative permittivity. This extension is validated for ionic liquids by comparison with a reference model from the literature and, in contrast to similar extensions, also applied to conventional salts with small spherical ions in aqueous, mixed and non-aqueous solvents. The central novelty is the inclusion of a modified parameter of closest approach, which improves the overall qualitative performance of the Pitzer-Debye-Hückel term over the complete relative permittivity range. Gibbs-Duhem consistency is retained in the modified extension and sample calculations for aqueous [BMIM][BF4] and aqueous NaCl are provided. The novel, modified and extended term with concentration dependent properties is combined with the predictive COSMO-RS-ES model for the calculation of phase equilibria and activity coefficients in electrolytes with conventional salts. The performance of the COSMO-RS-ES model for predictions of salt solubility in fully non-aqueous media improves significantly upon introduction of concentration dependent properties within the long-range electrostatics. Modelling performance with the modified extended Pitzer-Debye-Hückel term outperforms modelling with the unmodified extension as well as with the conventional term with no extension. The correlated relative permittivity of the mixture is overestimated with respect to experimental values and kinetic depolarization effects provide a plausible explanation for this observation. Overall, our results support the consistent introduction of concentration dependent properties within the electrostatic theory in order to improve the modelling of electrolytes with particular emphasis on non-aqueous electrolytes.

cond-mat.soft↗

arXiv2023

Thermodynamic and Transport Properties Modeling of Deep Eutectic Solvents: A review on gE-models, equations of state and molecular dynamics

Deep eutectic solvents (DESs) have gained attention in recent years as attractive alternatives to traditional solvents. There is a growing number of publications dealing with the thermodynamic modeling of DESs highlighting the importance of modeling the solutions' properties. In this review, we summarize the state-of-the-art in DES modeling as well as its current challenges. We also summarize the various modeling approaches to phase equilibria and properties of DESs with gE-models, EOS and molecular dynamics (MD) simulations. The current gE-model and EOS-based approaches handle DESs as pseudo-components in order to simplify the parameterizations and calculation strategies. However, for the models to become more transferable and predictive, it would be preferable to model the individual DES constituents instead of using the pseudo-components. This implies that validation with more detailed experimental data that includes the distribution of the DES components is also required. MD simulations, in contrast to gE-models and EOS, are capable of providing information about the liquid structure and can predict dynamic properties although, the latter quantities still show some imprecisions. Therefore, insights into the liquid structure of DES systems from MD could also aid in improving present modeling strategies in addition to a better understanding. Finally, the latest developments for DES force fields are discussed as the quality of the applied force fields determine the results of MD simulations.

physics.chem-ph↗