Joachim Gross

Joachim Gross
Universität Stuttgart · Institute of Thermodynamics and Thermal Engineering

Professor

About

182
Publications
18,464
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8,379
Citations
Citations since 2017
79 Research Items
4571 Citations
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800

Publications

Publications (182)
Article
Perturbation theories for fluids of molecules with soft-repulsive cores, such as the Lennard-Jones fluid, are usually based on the description of a fluid of hard spheres of temperature-dependent, and sometimes also density-dependent, diameter. The results obtained from such theories are typically rather sensitive towards the value of this diameter....
Article
Full-text available
It is generally not straightforward to apply molecular-thermodynamic theories to fluids with short-ranged attractive forces between their constituent molecules (or particles). This especially applies to perturbation theories, which, for short-ranged attractive fluids, typically must be extended to high order or may not converge at all. Here, we sho...
Article
Modern equations of state for real nonspherical molecules are often based on Wertheim’s first-order thermody- namic perturbation theory (TPT1). A major drawback of TPT1 is that it assumes tangentially bonded spheres. In this work, we develop a Helmholtz energy functional for systems comprising hard heterosegmented chains with arbitrary bond lengths...
Article
Sorption of gases in micro- and mesoporous materials is typically interpreted on the basis of idealized structural models where real structure effects such as defects and disorder are absent. For covalent organic frameworks (COFs) significant discrepancies between measured and simulated adsorption isotherms are often reported but rarely traced back...
Chapter
This chapter discusses thermodynamic properties and phase equilibria using equations of states. Focus is thereby placed on the perturbed-chain statistical associating fluid theory (PC-SAFT) as a representative for physically-based equations of state. It is a model that is suitable for nonspherical molecules and hydrogen-bonding species or mixtures....
Article
Full-text available
We develop a simplification of our recently proposed uf-theory for describing the thermodynamics of simple fluids and fluids comprising short chain molecules. In its original form, the uf-theory interpolates the Helmholtz energy between a first-order f-expansion and first-order u-expansion as (effective) lower and upper bounds. We here replace the...
Preprint
Sorption of gases in micro- and mesoporous materials is typically interpreted on the basis of idealized structural models where real structure effects such as defects and disorder are absent. For covalent organic frameworks (COFs) significant discrepancies between measured and simulated adsorption isotherms are often reported but rarely traced back...
Article
Industrial applications such as batteries and bio-separations require modeling the thermodynamic properties of mixed solvent electrolytes. Thermodynamic models for electrolytes often consider the solvents as a dielectric continuum characterized by their dielectric constant. Therefore, accurate predictions require a physically sound model for the di...
Article
Dynamic density functional theory (DDFT) allows the description of microscopic dynamical processes on the molecular scale extending classical DFT to non-equilibrium situations. Since DDFT and DFT use the same Helmholtz energy functionals, both predict the same density profiles in thermodynamic equilibrium. We propose a molecular DDFT model, in this...
Article
A classical density functional theory (cDFT) based on the PC-SAFT equation of state is proposed for the calculation of adsorption equilibria of pure substances and their mixtures in covalent organic frameworks (COFs). Adsorption isotherms of methane, ethane, n-butane and nitrogen in the COFs TpPa-1 and 2,3-DhaTph are calculated and compared to resu...
Article
Full-text available
We propose a predictive Density Functional Theory (DFT) for the calculation of solvation free energies. Our approach is based on a Helmholtz free-energy functional that is consistent with the perturbed-chain SAFT (PC-SAFT) equation of state. This allows a coarse-grained description of the solvent, based on an inhomogeneous density of PC-SAFT segmen...
Preprint
Full-text available
A classical density functional theory (cDFT) based on the PC-SAFT equation of state is proposed for the calculation of adsorption equilibria of pure substances and their mixtures in covalent organic frameworks (COFs). Adsorption isotherms of methane, ethane, n-butane and nitrogen in the COFs TpPa-1 and 2,3-DhaTph are calculated and compared to resu...
Preprint
Full-text available
We propose a predictive Density Functional Theory (DFT) for the calculation of solvation free energies. Our approach is based on a Helmholtz free-energy functional that is consistent with the perturbed-chain SAFT (PC-SAFT) equation of state. This allows a coarse-grained description of the solvent, based on an inhomogeneous density of PC-SAFT segmen...
Article
This study analyzes the adsorption behavior in two-dimensional heterogeneous slit pores using nonlocal density functional theory based on the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state. Both chemical heterogeneity and surface roughness on small atomistic scales are investigated. The solid structure is considere...
Article
Full-text available
We propose a new first-order perturbation theory that provides a near-quantitative description of the thermodynamics of simple fluids. The theory is based on the Ansatz that the Helmholtz free energy is bounded below by a first-order Mayer-f expansion. Together with the rigorous upper bound provided by a first-order u-expansion, this brackets the a...
Article
Organic Rankine Cycles transform low-temperature heat from sustainable sources into electrical power. Exploiting the full potential of a low-temperature heat source requires the optimal combination of Organic Rankine Cycles and working fluid. Today, working fluids are commonly pure components. However, mixtures can significantly improve the process...
Chapter
Solvents are key to many chemical processes. To find optimal combinations of solvents and processes, solvent and process design have to be integrated. In this work, we present a method for the integrated thermo-economic design of separation processes and solvents that achieves a high level of the desired integration. The method is based on our 1-st...
Article
This work proposes perturbation approaches for describing dipolar fluids as well as model and aqueous electrolyte solutions. The electrostatic pair potentials are split into short- and long-ranged contributions, whereas a third order perturbation expansion is applied for the short-ranged potentials. This circumvents the problem of divergent correla...
Article
Reliable prediction of transport coefficients for fluids, such as viscosity, thermal conductivity and diffusion coefficient, is an important prerequisite for process design. Besides experimental measurements and semi-empirical correlations, molecular simulations are a promising method to estimate transport properties of fluids over wide ranges of t...
Article
Understanding suitable boundary conditions for vapor-liquid interfaces is important for the development of physically realistic simulations of evaporation and condensation processes. This work addresses the question whether the inclusion of interfacial temperature jumps is necessary in the modeling of droplet evaporation or condensation. The analys...
Article
This study investigates the equivalence or differences between classical force fields with rigid bond lengths and the same models but with (harmonic) bond length potentials. For ethane, propane, and dimethyl ether described with the Transferable Anisotropic Mie potential, we vary the force constant of the harmonic bond length potentials and analyze...
Article
Application of classical density functional theory in cylindrical coordinates requires a fast Hankel transform algorithm of order zero and its inverse, when the involved convolution integrals are solved in Fourier space. Vector-valued fundamental measure theory requires a fast Hankel transform of first order and its inverse. Compared to naïve real...
Article
Entropy scaling has proven to be a powerful method for calculating transport properties. The applicability of the entropy scaling approach to predict the viscosity, thermal conductivity and self-diffusion coefficients of pure substances based on substance-specific parameters was over last years convincingly demonstrated in literature. In this work...
Article
The thermal conductivity of gases depends strongly on the vibrational and rotational degrees of freedom of the molecule under consideration. Entropy scaling is based on the residual entropy, which does not capture the intramolecular and rotational contributions. This study proposes a model for the thermal conductivity that accounts for these degree...
Article
Full-text available
We develop a perturbation theory for the difference between the Helmholtz energy of a Stockmayer fluid, i.e., a fluid interacting by a Lennard-Jones plus point-dipole potential, and a Lennard-Jones fluid. We show that the difference can be approximated by the perturbational Helmholtz energy contribution of a dipolar hard-sphere fluid with a suitabl...
Article
Classical density functional theory (DFT) is a powerful tool for studying solvation or problems where resolution of interfacial domains or interfacial properties among phases (or thin films) is required. Many interesting problems necessitate multi-dimensional modeling, which calls for robust and efficient algorithmic implementations of the Helmholt...
Conference Paper
Full-text available
Droplet evaporation within combustion chambers is of high importance for stable and efficient combustion. For ambient pressures exceeding the critical pressure of the injected fuel, evaporation processes are not fully understood yet. Especially the temperature evolution of the injected fuel is a key parameter to understand the transition of near cr...
Article
This study gives an assessment of the predictive capability of classical density functional theory (DFT) for adsorption processes of pure substances and mixtures of spherical and non-spherical molecular species. A Helmholtz energy functional based on the perturbed-chain statistical associating fluid theory (PC-SAFT) is applied to calculate isotherm...
Article
A thermodynamically consistent numerical framework for the simulation of three-dimensional sublimation processes of ice at temperatures below the triple point and low pressure is presented. To this end, a novel description of the local thermodynamic equilibrium of frozen water (ice) and a mixture of water vapour and an inert gas is derived, where a...
Article
This work extends Wertheim’s Thermodynamic Perturbation Theory (TPT) to include dimer-dimer graphs, i.e., we extend the theory beyond the so-called single-chain approximation. The theory is referred to as thermodynamic perturbation dimer theory. We provide a graph-theoretical derivation of the additional dimer-dimer term and resum the graphs in ter...
Article
In this work we present a methodology to determine phase coexistence lines for atomic and rigid molecular systems with an emphasis on solid-fluid and on solid-solid equilibria. Phase coexistence points are found by computing the absolute free energy for each candidate phase separately. For solid phases a combination of the extended Einstein crystal...
Conference Paper
In modern gas turbines and internal combustion engines, fluids are injected at high pressures, at fuel states either close to or exceeding the critical point. Accurate prediction of these processes require increasingly precise modelling of evaporating drops. Especially the transition of classical two phase evaporation to single phase dense fluid mixi...
Article
This special topics issue offers a broad perspective on the recent developments and reviews of state-of-the-art particle methods in science and engineering applications. This issue grew out of contributions delivered during the closing conference of the Collaborative Research Centre (CRC) 716 that for the last twelve years was contributing importan...
Article
Parameterization of classical force fields often suffers from highly correlated parameters. In the present work the hypothesis that transport properties such as shear viscosity or self-diffusion coefficient can be used to decouple force field parameters that were fitted to static thermodynamic properties, such as saturation vapor pressure and liqui...
Article
This study proposes a Polarizable Transferable Anisotropic Mie (P-TAMie) force field for ethers and mixtures of ethers with n-alkanes and nitrogen. In our approach polarizability is accounted for using a charge-on-spring model (also referred to as Drude model or core-shell model) placed on every united atom site. Parameters for polarizabilities are...
Article
In this work, we report comprehensive molecular simulation data for the Helmholtz energy, the internal energy, the constant-volume heat capacity, and the relative permittivity of pure nonpolarizable dipolar hard spheres. The dimensionless density (?) thereby covers a range from 0.05 to 1.0, and dimensionless squared dipole moments (μ ² ) range from...
Article
The transferable anisotropic Mie potential (TAMie) force field is extended to acetates and formates. Intramolecular bending and torsion potentials were obtained from quantum chemical calculations. The parameters defining the Mie pair potential, representing the van der Waals interactions, as well as point charges were optimized. These force field p...
Article
Density gradient theory has become an important tool for calculating the surface tension of pure components as well as mixtures. The calculation requires knowledge about the so-called influence parameter. Since in most applications this parameter is obtained by fitting results of the density gradient theory to experimental data for surface tensions...
Article
The Wolf method for calculation of electrostatic interactions in molecular simulations is known to describe the energy well, whereas the forces have discontinuities. For a more reliable description of the forces this method can be extended with a shifted force approach. This leads to a good description of the forces and precise molecular dynamics s...
Article
This study demonstrates the capability of the DFT formalism to predict contact angles and density profiles of model fluids and of real substance in good quantitative agreement to molecular simulations and to experimental data. The DFT problem is written in cylindrical coordinates and the solid-fluid interactions are defined as external potentials t...
Article
The present work summarises the main findings of a systematic study on the behaviour of liquid droplets embedded in a high pressure and temperature environment. Thanks to the availability of quantitative temperature data, it was possible for the first time to assess the conceptual soundness of different theoretical approaches. In all cases, the pre...
Article
This study proposes a model for self-diffusion coefficients of pure substances from entropy scaling using the Perturbed-Chain Polar Statistical Associating Fluid Theory (PC-SAFT) equation of state. In accordance with the entropy scaling approach proposed by Y. Rosenfeld [Phys. Rev. A 1977, 15, 2545-2549], we observe that the self-diffusion coeffici...
Article
A meaningful parameterization of an analytic equation of state can be obtained by adjusting the pure component parameters to vapor pressure data and to liquid density data of the considered pure substance. For substances, where no vapor pressure data is available the parameterization of an equation of state is more subtle. In this study we investig...
Article
In this work, we develop and analyze a third order and a fourth order perturbation theory for non-polarizable dipolar hard spheres. The electrostatic potential is split into a short-ranged and a long-ranged part. A perturbation expansion is applied for the short-ranged potential where the contribution of higher order terms is approximated through a...
Article
In this work, the heterosegmented GC-PC-SAFT model is parameterized for branched alkanes. Branched alkanes can be regarded as the skeleton of more complex molecules. Analyzing experimental data of branched alkanes in comparison to the linear analogous gives rationale to decisions about what substances require a more refined or individualized parame...
Article
A Helmholtz energy functional consistent with the heterosegmented group-contribution perturbed-chain polar statistical associating fluid theory (GC-PCP-SAFT) is developed in this study and is applied to predict interfacial properties of planar vapor-liquid interfaces. Predicted surface tensions of pure substances are in very good agreement with exp...
Article
The curvature dependence of interfacial properties has been discussed extensively over the last decades. After Tolman published his work on the effect of droplet size on surface tension, where he introduced the interfacial property now known as Tolman length, several studies were performed with varying results. In recent years, however, some consen...
Article
A modification of the Wolf method [J. Chem. Phys., 110, 8254-8282 (1999)], a spherically truncated pairwise summation to evaluate electrostatic interactions efficiently, is proposed. This method achieves better results for the energy and the approach is used for determining phase equilibria in the grand canonical ensemble. To assess optimal paramet...
Article
This study proposes a simple model for viscosities, based on entropy scaling, for real substances and mixtures. The residual entropy is calculated with the perturbed chain polar statistical associating fluid theory (PCP-SAFT). The model requires two or three pure component parameters, noting, however, that an entirely predictive group-contribution...
Article
The objective of this study is to determine the Lifshitz–van der Waals/Acid–Base (LW/AB) surface energy components of urea–water solutions (UWS) for different urea mass fractions. The surface energy parameters are evaluated by ring tensiometry and contact angle measurements of sessile drops placed onto pre-determined solid substrates. Therefore, th...
Article
Transferable force fields allow the prediction of physical properties for substances with scarce or absent experimental data. For substances with a comprehensive experimental database, however, transferable force fields produce results with higher errors than desired, because the transferable force fields are designed to represent a compromise in c...
Article
This study compares surface tensions as calculated from the classical density functional theory (DFT) and from density gradient theory (DGT) to experimental data. This comparison is inevitably not on equal ground, because the DFT is purely predictive for interfacial properties, both for pure substances and for mixtures, whereas DGT requires an adju...
Article
Spontaneous imbibition in cellulosic materials is an expanding field of research due to the direct applicability in paper-based microfluidics. Here, we show experimentally, using simultaneous thermal and optical imaging that the temperature at the wetting front during capillary filling of paper is temporarily increased, even if the imbibed fluid an...
Article
The van der Waals contribution of force fields designed for calculating phase equilibria and thermodynamic properties are usually adjusted to experimental data of pure components. Using these force fields for mixtures by applying combining rules for the cross-wise interaction potentials does not always lead to satisfactory results. This study consi...
Conference Paper
Full-text available
The disintegration process of liquid fuel within combustion chambers is one of the most important parameters forefficient and stable combustion. Especially for high pressures exceeding the critical value of the injected fluids the mixing processes are not fully understood yet. Recently, different theoretical macroscopic models have been introduced...
Article
Full-text available
To exploit the full thermo-economic potential of an Organic Rankine Cycle (ORC), the process, equipment and working fluid have to be optimized simultaneously. Today, working fluid selection and thermo-economic process optimization are commonly separated. This separation leads to suboptimal solutions if the prior working fluid selection fails. In th...
Article
Full-text available
Organic Rankine Cycles (ORC) transform low-temperature heat into electrical power. To make best use of a heat source, ORC process and working fluid have to be optimized simultaneously. Thus, integrated design approaches of fluids and processes have been developed. However, integrated design approaches are usually complex and based on specific softw...
Article
Full-text available
The Helmholtz energy of a fluid interacting by a Lennard-Jones pair potential is expanded in a perturbation series. Both the methods of Barker-Henderson (BH) and of Weeks-Chandler-Andersen (WCA) are evaluated for the division of the intermolecular potential into reference and perturbation parts. The first four perturbation terms are evaluated for v...
Article
Full-text available
The right molecules are often the key to overall process performance and economics of many energy and chemical conversion processes, such as e.g., solvents for CO2 capture or working fluids for Organic Rankine Cycles. However, the process settings also impact the choices on the molecular level. Thus, ultimately, the process and the molecules have t...
Article
The perturbed-chain polar statistical associating fluid theory (PCP-SAFT) and density gradient theory are used to calculate interfacial properties of multicomponent systems. The constant influence parameters are adjusted to experimental surface tension data of pure fluids and the cross-influence parameters are determined from a geometric combining...
Article
Entropy scaling is an intriguingly simple approach for correlating and predicting transport properties of real substances and mixtures. It is convincingly documented in the literature that entropy scaling is indeed a firm concept for the shear viscosity of real substances, including hydrogen bonding species and strongly nonspherical species. We inv...
Article
This study compares different algorithms for solving the equations of classical density functional theory for the one-dimensional vapor-liquid interface of real fluids: Picard iteration, Anderson mixing, a restarted quasi Newton method and two versions of the matrix-free inexact Newton method, one using analytic the other using numerically approxim...
Article
A Helmholtz energy functional based on the Perturbed-Chain Polar Statistical Associating Fluid Theory (PCP-SAFT) Equation of State is proposed. A weighted density approximation is used to develop two variants of dispersion functionals. We conduct molecular simulations (Monte Carlo) in order to assess both models. The structure of thin liquid adsorb...
Chapter
Organic Rankine Cycles (ORCs) generate electrical power from low-temperature heat. To exploit the full potential of a heat source, the cycle has to be tailored to the specific application. In this work, we present an approach for the integrated thermo-economic design of ORC process, working fluid and equipment based on a single thermodynamic model....
Chapter
Organic Rankine Cycles (ORC) can transform low-temperature heat into electrical power. To ensure optimal use of a heat source, process and working fluid need to be tailored to the specific application. We present a one-stage approach for the integrated design of ORC process and working fluid, which identifies the optimal working fluid and the corre...
Article
The Transferable Anisotropic Mie potential (TAMie) is extended to ketones, aldehyhdes and small cyclic alkanes. Parameters defining the Mie pair potential, representing van der Waals interactions, as well as partial point charges were treated as adjustable. These adjustable parameters were identified by minimizing deviation of calculated vapor pres...
Article
In this work, we conduct a comprehensive simulation study on Helmholtz energies for non-primitive model electrolyte solutions in order to assess fluid theories. Simulation data is obtained with two different methods. Using a new thermodynamic integration path, we calculate Helmholtz energy contributions arising from damped, short-ranged electrostat...
Article
Objective measures to compare the adequacy of models can be very useful to guide the development of thermodynamic models. Thermodynamicists are frequently faced with the so-called bias-variance dilemma, where one model may be less accurate in correlating experimental data but more robust in extrapolations than another model. In this work, we use Ba...
Article
Three-body interactions constitute an important part of the effective potential between nanocrystals (NCs). In this study, molecular dynamics simulations are conducted on gold NCs capped with alkyl thiol ligands in vacuum. Over the course of a simulation performed in two- and three-body systems, we measure the forces acting on the cores of the NCs....
Article
The Thermodynamic Perturbation Theory (TPT) developed by Michael S. Wertheim in the years 1984–1986 provides a powerful framework for modeling directional attractive interactions. TPT is successful, for example, in describing fluids with hydrogen-bonding interactions and it leads to accurate models of non-spherical chain fluids. The theory of Werth...
Article
Mixtures of charged and dipolar hard spheres are important models for electrolyte solutions, in particular for developing molecular-based fluid theories. This study presents data for the ionic chemical potential from Monte Carlo simulations for mixtures where charged and dipolar hard spheres have the same diameter. Earlier simulation studies of thi...
Article
Full-text available
Organic Rankine Cycles (ORC) transform low-temperature heat into electrical power. To exploit the full potential of a low-temperature heat source, the ORC system is tailored to the specific application. Tailoring an ORC system is challenging, since both process and working fluid have to be optimized simultaneously. We present an approach for integr...
Article
We derive two new equations of state for linear, flexible hard-chain fluids based on Wertheim's Thermodynamic Perturbation Theory (TPT) of third order. The 4-particle distribution function in the third-order term is first approximated solely by 2- and 3-particle distribution functions and is then refined by adjusting an expression to results of mol...
Article
Statistical Associating Fluid Theory (SAFT) equations of state (EoS) for mixtures require cross-interaction parameters. For real systems, combining rules, such as the Lorenz-Berthelot combining rules, have to be corrected using at least one binary interaction parameter, kij. Values of kij are usually adjusted to experimental data of phase equilibri...
Article
We present an approach to calculate interfacial resistivities against mass and heat transfer at a vaporliquid interface. Classical density functional theory is combined with the perturbed chain statistical associating fluid theory (PC-SAFT) equation of state to calculate continuous density profiles and (partial molar) enthalpy profiles across the i...
Article
A new transferable force field parametrization for n-alkanes and n-olefins is proposed in this work. A united-atom approach is taken, where hydrogen atoms are lumped with neighboring atoms to single interaction sites. A comprehensive study is conducted for alkanes, optimizing van der Waals force field parameters in 6 dimensions. A Mie n-6 potential...
Article
In this work, we propose a new predictive entropy-scaling approach for Newtonian shear viscosities based on group contributions. The approach is based on Rosenfelds original work [ Rosenfeld, Y. Phys. Rev. A 1977, 15, 2545-2549 ]. The entropy scaling is formulated as third order polynomial in terms of the residual entropy as calculated from a group...
Article
Full-text available
We study the isotropic (vapor and liquid) phase behavior of attractive chain fluids. Special emphasis is placed on the role of molecular flexibility, which is studied by means of a rod-coil model. Two new equations of state (EoSs) are developed for square-well- (SW) and Lennard-Jones (LJ) chain fluids. The EoSs are developed by applying the perturb...
Article
Full-text available
We develop an equation of state (EoS) for describing isotropic-nematic (IN) phase equilibria of Lennard-Jones (LJ) chain fluids. The EoS is developed by applying a second order Barker-Henderson perturbation theory to a reference fluid of hard chain molecules. The chain molecules consist of tangentially bonded spherical segments and are allowed to b...
Article
In this study we propose using an analytical equation of state for guiding molecular simulations in the grand canonical ensemble. Molecular simulations in the grand canonical ensemble deliver phase equilibrium properties with low statistical uncertainty. The entire phase envelope can be obtained, when histograms of several simulations along the pha...
Article
Computer-aided molecular design allows generating novel fluids fulfilling a set of target properties. An integrated design of fluid and process directly employs a process-based objective function. In this work, we solve the integrated process and fluid design problem using the continuous-molecular targeting computer-aided molecular design (CoMT-CAM...

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