# H.-O. May's research while affiliated with Evangelische Hochschule Darmstadt and other places

## Publications (27)

Article
The three-dimensional Gaussian core model (GCM) for soft-matter systems has repulsive interparticle interaction potential ϕ(r)=εexp[−(r/σ)2], with r the distance between a pair of atoms, and the positive constants ε and σ setting the energy and length scales, respectively. ϕ(r) is mostly soft in character, without the typical hard core present in f...
Preprint
The three-dimensional Gaussian core model (GCM) for soft-matter systems has repulsive interparticle interaction potential $\phi (r) = \varepsilon\, {\rm exp}\left[ -(r/\sigma)^{2} \right]$, with $r$ the distance between a pair of atoms, and the positive constants $\varepsilon$ and $\sigma$ setting the energy and length scales, respectively. $\phi (... Article Liquid water has anomalous liquid properties, such as its density maximum at 4 °C. An attempt at theoretical explanation proposes a liquid-liquid phase transition line in the supercooled liquid state, with coexisting low-density liquid (LDL) and high-density liquid (HDL) states. This line terminates at a critical point. It is assumed that the LDL s... Preprint Liquid water has anomalous liquid properties, such as its density maximum at 4\degree C. An attempt at theoretical explanation proposes a liquid-liquid phase transition line in the supercooled liquid state, with coexisting low-density (LDL) and high-density (HDL) liquid states. This line terminates at a critical point. It is assumed that the LDL st... Article The thermodynamic curvature scalar R is evaluated for supercooled water with a two-state equation of state correlated with the most recent available experimental data. This model assumes a liquid-liquid critical point. Our investigation extends the understanding of the thermodynamic behavior of R considerably. We show that R diverges to -∞ when app... Article We evaluate the thermodynamic curvature$R$for fluid argon, hydrogen, carbon dioxide, and water. For these fluids,$R$is mostly negative, but we also find significant regimes of positive$R$, which we interpret as indicating solid-like fluid properties. Regimes of positive$R\$ are present in all four fluids at very high pressure. Water has, in ad...
Article
Direct molecular-simulation results of the thermodynamic Grüneisen parameter, γG, and the density scaling exponent, γ, are reported for the Lennard-Jones and the Gaussian core model potential in extended fluid-phase regions, and are compared with results calculated from equations of state. The direct molecular simulation method is based on the calc...
Article
The thermodynamic curvature scalar R for the Lennard-Jones system is evaluated in phase space, including vapor, liquid, and solid state. We paid special attention to the investigation of R along vapor-liquid, liquid-solid, and vapor-solid equilibria. Because R is a measure of interaction strength, we traced out the line R=0 dividing the phase space...
Article
Evaluation of the fluid properties obtained from thermodynamic derivatives is a critical test for any equation of state, especially in the vicinity of the critical point. This is a state region of great importance for the nonclassical gas dynamics of dense vapors with unconventional dynamic phenomena. In this study, the isobaric and isochoric heat...
Article
The behavior of thermodynamic response functions and the thermodynamic scalar curvature in the supercritical region have been studied for a Lennard-Jones fluid based on a revised modified Benedict-Webb-Rubin equation of state. Response function extrema are sometimes used to estimate the Widom line, which is characterized by the maxima of the correl...
Article
The thermodynamic excess properties for the Gaussian core model (GCM) fluid are calculated from an equation of state for the pressure and the internal energy. The equation of state is obtained from extensive Monte Carlo simulation data. Entropy–energy correlations as well as Rosenfeld's scaling laws for the temperature dependence of the excess entr...
Article
In this study, we investigate the self-diffusion coefficient, the shear viscosity and the thermal conductivity of a single-component system interacting via a Gaussian core (GC) potential. The transport properties are studied by means of the Green-Kubo formulas calculated from molecular dynamics simulation. We show that, for certain state conditions...
Article
By means of molecular dynamics simulations we investigate the Stokes–Einstein behaviour of the Gaussian Core Model liquid at high densities. From a recent analysis at moderately high densities, we found that the Stokes–Einstein factor grows linearly with the viscosity. We show that at high densities the behaviour is similar, but there are slight de...
Article
We investigated transport coefficients of a single-component system interacting via a Gaussian core potential. Anomalies were produced due to the fact that the potential is bounded and penetration of particles occurs. The self-diffusion coefficient, the viscosity and the thermal conductivity were studied by means of the Green-Kubo formulas calculat...
Article
The Stokes-Einstein relation between shear viscosity, diffusion constant, and temperature holds in many liquids, but there are certain examples where the relation fails. In this study, we consider liquids where the interaction potential is bounded, and we find that a different behavior of the Stokes-Einstein relation is possible, where the relation...
Article
By means of molecular dynamics simulations we investigated the shear viscosity of the Gaussian Core Model fluid. We observed anomalous viscous behaviour for dimensionless densities greater than 0.3 and dimensionless temperatures below 0.04. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Article
We investigated static and dynamic liquid-state anomalies of a single-component system interacting via a Gaussian core potential. Anomalies are produced due to the fact that the potential is bounded. Based on standard Monte Carlo simulations, we developed an equation of state for an extended phase space. From this, we were able to derive anomalies...
Article
By means of molecular dynamics simulation we investigate the diffusion behaviour of a fluid system interacting via a Gaussian core pair potential. We observe anomalous diffusion when the dimensionless density becomes larger than 0.35. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Article
By means of three-dimensional Monte Carlo simulations for a N,V ,T –ensemble we investigate the phasebehaviour of a fluid system interacting via a “Mexican Hat”–pair potential for a very large temperature and density range.
Article
We investigate the phase behaviour of a single-component system in three dimensions (3D). The particles are interacting via a core-softened shoulder potential. Using standard N,V,T Monte Carlo and Gibbs-ensemble simulations, we obtain the complete gas–liquid phase behaviour, the coexistence line and the gas–liquid critical point in 3D for this pote...
Article
Investigations for one– and two–dimensional systems have shown that the Stell–Hemmer potential can produce liquid–state anomalies. By means of a Monte Carlo simulation for a N; V; T–ensemble we calculate the phase behaviour and show that these anomalies disappear in three dimensions.
Article
By means of a Gibbs ensemble Monte Carlo method we calculate the gas-liquid coexistence line for a Stell-Hemmer fluid in three dimensions. We estimate the critical point using a scaling law where the critical exponent is β = 0.32.

## Citations

... This quantity contains rich information on the underlying fluctuations. Subsequently, [1, [4][5][6][7][8] employ this geometrically motivated thermodynamic fluctuation theory to several open thermodynamic systems such as ideal gases, paramagnets, Van der Waals gases, fluids with single or multiple components. In fluids, the curvature is strongly correlated with the nature of interactions with a reversal in sign through critical values. ...
... The Maxwell and Ricci phase boundaries are tangent to each other at the critical point. Our plots in Figs. 5 and 6 are qualitatively similar to the calculated Maxwell phase boundary of more practical fluid models 23,65 . It seems then that this agreement of the Maxwell and Ricci phase boundaries near the critical point is a property of a large group of systems, if not universal. ...
... LJ EOS that are empirically based are those of Refs. [28,41,51,53,[60][61][62][63][64][65]. The remaining LJ EOS considered in the present work [52,54,55,[66][67][68][69] are denoted here as semi-theoretical. ...
... One of the more recent proposals for a Widom line is the R-Widom line, defined as the locus of maxima of the isotherms of the scalar curvature of TG [16,17]. There are several proposals for a geometrical description of thermodynamics based mainly on fluctuation theory [18][19][20][21][22][23][24][25]. ...
... Other interesting phenomena have been explored with the geometry of thermodynamics. Supercooled water [26,27] near a conjectured second critical point in the metastable liquid phase is one such case. More recently, the thermodynamic Ricci curvature scalar R has been evaluated for cases having a full three dimensional Riemannian geometry [28][29][30][31] . ...
... Since the introduction of the Ruppeiner metric in 1979 7 , a substantial body of work [12][13][14][15] has been directed towards firming up its theoretical groundwork as well as developing its possible applications. The Ruppeiner metric has found many important applications in the field of thermal physics, such as in fluctuation theory 14 , finite-time thermodynamics [16][17][18] , phase transitions 15,[19][20][21][22][23][24][25][26] , and even black hole thermodynamics [25][26][27] , among others. In this work, we focus on phase transitions. ...
... The use of the Gr€ uneisen parameter in fluid dynamics theory is quite limited, 44,45 and systematic studies involving G are limited to liquid flows. 46,47 Recently, Mausbach et al. 43 examined the variation of the Gr€ uneisen parameter over the temperature-entropy diagram for 28 pure fluids. ...
... Interestingly, numerous recent studies are focused on understanding the phenomenological properties of the black hole microstructure in AdS spacetime, via the phase transition study . These efforts are inspired by the applications of the Ruppeiner geometry to the conventional thermodynamic systems [33][34][35][36][37]. However, in the context of black hole thermodynamics, there is a significant difference in the approach. ...
... Since the particle are soft, the potential takes a finite value for r = 0, and at high density, particle overlapping shall result in nontrivial sources of entropic increase, which may exceed the associated energetic cost. Although this effect is well-known in suspensions of soft spheres [44][45][46][47], its relevance in the present context is not clear, and we will leave this regime aside from our analysis. ...
... To evaluate the thermodynamic geometry in (T , ρ) coordinates requires that we know the fundamental equation f (T , ρ) . May and Mausbach [53] found f (T , ρ) for the GCM by fitting the extensive computer simulation data by Mausbach and Sadus [44] . These computer simulations consisted of determining triplet values (T , ρ, p) on a grid. ...