Adsorption from Solution

A major problem of the thermodynamic theory of adsorption at the solid/liquid interface is concerned with the definition of the heterogeneous surface in terms of mathematically treatable model. The paper gives a review of the theoretical approaches applied to studies of adsorption from concentrated and diluted binary mixtures. Experimental work has enjoyed much success since the uniform surface, graphitized carbon blacks became available. Results are described and discussed of measurements of heats of immersion on such surfaces

Adsorption from Solution

A major problem of the thermodynamic theory of adsorption at the solid/liquid interface is concerned with the definition of the heterogeneous surface in terms of mathematically treatable model. The paper gives a review of the theoretical approaches applied to studies of adsorption from concentrated and diluted binary mixtures. Experimental work has enjoyed much success since the uniform surface, graphitized carbon blacks became available. Results are described and discussed of measurements of heats of immersion on such surfaces

A Study of the Mechanism of Micropore Filling. I. Molecular Sieve Effects

The adsorptive properties of two microporous carbons and a microporous silica have been investigated and compared using argon and benzene. The micropore volumes determined using the Theory for Volume filling of Micropores (TVFM) agreed to within 40/o of the total micropore volumes determined from the a8 method of pore analysis. Adsorption data of argon at 77 °K and benzene at 298 °K on the microporous carbons were interpreted in terms of the Dubinin-Astakhov and Dubinin-Radushkevich equations, and Weibull and Gaussian distributions of the adsorption free energy with pore volume, respectively. The Weibull distribution was found to apply better than the Gaussian distribution, although variations from linear D-A plots occurred. The adsorption data on the silica sample were best interpreted as a two-term D-R equation. Plots of the distribution of adsorption energy with pore volume of the silica sample for each term of the D-R equation and their effective contribution to the cumulative distribution curve gave conclusive evidence of the ordering of the adsorption process within micropores of varying dimensions

Gas-Liquid Nucleation in Two Dimensional System

We study the nucleation of the liquid phase from a supersaturated vapor in two dimensions (2D). Using different Monte Carlo simulation methods, we calculate the free energy barrier for nucleation, the line tension and also investigate the size and shape of the critical nucleus. The study is carried out at an intermediate level of supersaturation(away from the spinodal limit). In 2D, a large cut-off in the truncation of the Lennard-Jones (LJ) potential is required to obtain converged results, whereas low cut-off (say, $2.5\sigma$ is generally sufficient in three dimensional studies, where $\sigma$ is the LJ diameter) leads to a substantial error in the values of line tension, nucleation barrier and characteristics of the critical cluster. It is found that in 2D, the classical nucleation theory (CNT) fails to provide a reliable estimate of the free energy barrier. It underestimates the barrier by as much as 70% at the saturation-ratio S=1.1 (defined as S=P/PC, where PC is the coexistence pressure at reduced temperature $T^{\star}= 0.427$). Interestingly, CNT has been found to overestimate the nucleation free energy barrier in three dimensional (3D)systems near the triple point. In fact, the agreement with CNT is worse in 2D than in 3D. Moreover, the existing theoretical estimate of the line tension overestimates the value significantly.Comment: 24 pages, 8 figure

Sorption of Water and Polar-Nonpolar Organic Vapors on Microporous Chromia

High surface area, narrow particle size distribution chromic;t was investigated for its microporosity. Adsorption studies with argon, water vapor, methanol, isopropanol, butane, isobutane, neopentane, and heptane indicated alternative approaches to the determination of micropore volume

Improving Policy Learning via Language Dynamics Distillation

Recent work has shown that augmenting environments with language descriptions improves policy learning. However, for environments with complex language abstractions, learning how to ground language to observations is difficult due to sparse, delayed rewards. We propose Language Dynamics Distillation (LDD), which pretrains a model to predict environment dynamics given demonstrations with language descriptions, and then fine-tunes these language-aware pretrained representations via reinforcement learning (RL). In this way, the model is trained to both maximize expected reward and retain knowledge about how language relates to environment dynamics. On SILG, a benchmark of five tasks with language descriptions that evaluate distinct generalization challenges on unseen environments (NetHack, ALFWorld, RTFM, Messenger, and Touchdown), LDD outperforms tabula-rasa RL, VAE pretraining, and methods that learn from unlabeled demonstrations in inverse RL and reward shaping with pretrained experts. In our analyses, we show that language descriptions in demonstrations improve sample-efficiency and generalization across environments, and that dynamics modeling with expert demonstrations is more effective than with non-experts

Curvature Dependence of Surface Free Energy of Liquid Drops and Bubbles: A Simulation Study

We study the excess free energy due to phase coexistence of fluids by Monte Carlo simulations using successive umbrella sampling in finite LxLxL boxes with periodic boundary conditions. Both the vapor-liquid phase coexistence of a simple Lennard-Jones fluid and the coexistence between A-rich and B-rich phases of a symmetric binary (AB) Lennard-Jones mixture are studied, varying the density rho in the simple fluid or the relative concentration x_A of A in the binary mixture, respectively. The character of phase coexistence changes from a spherical droplet (or bubble) of the minority phase (near the coexistence curve) to a cylindrical droplet (or bubble) and finally (in the center of the miscibility gap) to a slab-like configuration of two parallel flat interfaces. Extending the analysis of M. Schrader, P. Virnau, and K. Binder [Phys. Rev. E 79, 061104 (2009)], we extract the surface free energy gamma (R) of both spherical and cylindrical droplets and bubbles in the vapor-liquid case, and present evidence that for R -> Infinity the leading order (Tolman) correction for droplets has sign opposite to the case of bubbles, consistent with the Tolman length being independent on the sign of curvature. For the symmetric binary mixture the expected non-existence of the Tolman length is confirmed. In all cases {and for a range of radii} R relevant for nucleation theory, gamma(R) deviates strongly from gamma (Infinity) which can be accounted for by a term of order gamma(Infinity)/gamma(R)-1 ~ 1/R^2. Our results for the simple Lennard-Jones fluid are also compared to results from density functional theory and we find qualitative agreement in the behavior of gamma(R) as well as in the sign and magnitude of the Tolman length.Comment: 25 pages, submitted to J. Chem. Phy

A Study of the Mechanism of Micropore Filling. I. Molecular Sieve Effects

The adsorptive properties of two microporous carbons and a microporous silica have been investigated and compared using argon and benzene. The micropore volumes determined using the Theory for Volume filling of Micropores (TVFM) agreed to within 40/o of the total micropore volumes determined from the a8 method of pore analysis. Adsorption data of argon at 77 °K and benzene at 298 °K on the microporous carbons were interpreted in terms of the Dubinin-Astakhov and Dubinin-Radushkevich equations, and Weibull and Gaussian distributions of the adsorption free energy with pore volume, respectively. The Weibull distribution was found to apply better than the Gaussian distribution, although variations from linear D-A plots occurred. The adsorption data on the silica sample were best interpreted as a two-term D-R equation. Plots of the distribution of adsorption energy with pore volume of the silica sample for each term of the D-R equation and their effective contribution to the cumulative distribution curve gave conclusive evidence of the ordering of the adsorption process within micropores of varying dimensions