Influence of orientational disorder in the adsorbent on the structure and dynamics of the adsorbate: MD simulations of SO2_2 in ZSM-22

Structural and dynamical behavior of SO$_2$ molecules within ZSM22 is studied using MD simulations, to understand the influence of orientational disorder (OD) and intercrystalline spacing in ZSM22 as a function of adsorbate loading. Addition of inter-crystalline space provides connectivity of isolated pores in ZSM22 and is shown to suppress both translational and rotational motion of SO$_2$. We infer that geometry and dimensionality of the connecting space is an important factor in determining the effects of pore connectivity on the adsorbed species behavior. As a function of OD, decrease in self diffusion coefficient of SO$_2$ in ZSM22 is observed. An increase in rotational correlation time t and a decrease in libration angle with OD is observed, due to the restriction imposed on the orientational freedom of the adsorbate by an increase in OD. The behavior of SO$_2$ result from an interplay of guest-host interactions and the dimensionality and confinement geometry.Comment: 24 pages with 6 figures in the main text and 4 figures in the supplement appended at the en

MLOps: A Review

Recently, Machine Learning (ML) has become a widely accepted method for significant progress that is rapidly evolving. Since it employs computational methods to teach machines and produce acceptable answers. The significance of the Machine Learning Operations (MLOps) methods, which can provide acceptable answers for such problems, is examined in this study. To assist in the creation of software that is simple to use, the authors research MLOps methods. To choose the best tool structure for certain projects, the authors also assess the features and operability of various MLOps methods. A total of 22 papers were assessed that attempted to apply the MLOps idea. Finally, the authors admit the scarcity of fully effective MLOps methods based on which advancements can self-regulate by limiting human engagement

Roulette-Wheel Selection-Based PSO Algorithm for Solving the Vehicle Routing Problem with Time Windows

The well-known Vehicle Routing Problem with Time Windows (VRPTW) aims to reduce the cost of moving goods between several destinations while accommodating constraints like set time windows for certain locations and vehicle capacity. Applications of the VRPTW problem in the real world include Supply Chain Management (SCM) and logistic dispatching, both of which are crucial to the economy and are expanding quickly as work habits change. Therefore, to solve the VRPTW problem, metaheuristic algorithms i.e. Particle Swarm Optimization (PSO) have been found to work effectively, however, they can experience premature convergence. To lower the risk of PSO's premature convergence, the authors have solved VRPTW in this paper utilising a novel form of the PSO methodology that uses the Roulette Wheel Method (RWPSO). Computing experiments using the Solomon VRPTW benchmark datasets on the RWPSO demonstrate that RWPSO is competitive with other state-of-the-art algorithms from the literature. Also, comparisons with two cutting-edge algorithms from the literature show how competitive the suggested algorithm is

Towards crystal structure prediction of complex organic compounds - a report on the fifth blind test

Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1: 1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories - a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome

CO2 Adsorption in Metal-Organic Framework Mg-MOF-74: Effects of Inter-Crystalline Space

Metal-Organic Frameworks (MOF) have been identified as highly efficient nanoporous adsorbents for CO2 storage. In particular, Mg-MOF-74 has been shown to promise exceptionally high CO2 sorption. Although several studies have reported adsorption isotherms of CO2 in Mg-MOF-74, the effect of inter-crystalline spacing in Mg-MOF-74 on the sorption of CO2 has not been addressed. These effects have been shown to be profound for a quadrupolar molecule like CO2 in the case of silicalite (Phys. Chem. Chem. Phys. 22 (2020) 13951). Here, we report the effects of inter-crystalline spacing on the adsorption of CO2 in Mg-MOF-74, studied using grand canonical Monte Carlo (GCMC) simulations. The inter-crystalline spacing is found to enhance adsorption at the crystallite surfaces. Larger inter-crystalline spacing up to twice the kinetic diameter of CO2 results in higher adsorption and larger crystallite sizes suppress adsorption. Magnitudes of the inter-crystalline space relative to the kinetic diameter of the adsorbed fluid and the surface to volume ratio of the adsorbent crystallites are found to be important factors determining the adsorption amounts. The results of this study suggest that the ideal Mg-MOF-74 sample for CO2 storage applications should have smaller crystallites separated from each other with an inter-crystalline space of approximately twice the kinetic diameter of CO2

Sorption, Structure and Dynamics of CO2 and Ethane in Silicalite at High Pressure: A Combined Monte Carlo and Molecular Dynamics Simulation Study

Silicalite is an important nanoporous material that finds applications in several industries, including gas separation and catalysis. While the sorption, structure, and dynamics of several molecules confined in the pores of silicalite have been reported, most of these studies have been restricted to low pressures. Here we report a comparative study of sorption, structure, and dynamics of CO2 and ethane in silicalite at high pressures (up to 100 bar) using a combination of Monte Carlo (MC) and molecular dynamics (MD) simulations. The behavior of the two fluids is studied in terms of the simulated sorption isotherms, the positional and orientational distribution of sorbed molecules in silicalite, and their translational diffusion, vibrational spectra, and rotational motion. Both CO2 and ethane are found to exhibit orientational ordering in silicalite pores; however, at high pressures, while CO2 prefers to reside in the channel intersections, ethane molecules reside mostly in the sinusoidal channels. While CO2 exhibits a higher self-diffusion coefficient than ethane at low pressures, at high pressures, it becomes slower than ethane. Both CO2 and ethane exhibit rotational motion at two time scales. At both time scales, the rotational motion of ethane is faster. The differences observed here in the behavior of CO2 and ethane in silicalite pores can be seen as a consequence of an interplay of the kinetic diameter of the two molecules and the quadrupole moment of CO2

Effect of Pore Connectivity on the Behavior of Fluids Confined in Sub-Nanometer Pores: Ethane and CO₂ Confined in ZSM-22

The behavior of fluids under nano-confinement varies from that in bulk due to an interplay of several factors including pore connectivity. In this work, we use molecular dynamics simulations to study the behavior of two fluids—ethane and CO2 confined in ZSM-22, a zeolite with channel-like pores of diameter 0.55 nm isolated from each other. By comparing the behavior of the two fluids in ZSM-22 with that reported earlier in ZSM-5, a zeolite with pores of similar shape and size connected to each other via sinusoidal pores running perpendicular to them, we reveal the important role of pore connectivity. Further, by artificially imposing pore connectivity in ZSM-22 via inserting a 2-dimensional slab-like inter-crystalline space of thickness 0.5 nm, we also studied the effect of the dimensionality and geometry of pore connectivity. While the translational motion of both ethane and CO2 in ZSM-22 is suppressed as a result of connecting the pores by perpendicular quasi-one-dimensional pores of similar dimensions, the effect of connecting the pores by inserting the inter-crystalline space is different on the translational motion of the two fluids. For ethane, pores connected via inter-crystalline space facilitate translational motion but suppress rotational motion, whereas in the case of CO2, both types of motion are suppressed by pore connection due to the strong interaction of CO2 with the surface of the substrate

High resolution spectral metrology leveraging topologically enhanced optical activity in fibers

Optical rotation in a medium, which is typically small, can be enhanced by harnessing spin-orbit interaction in fiber modes. Here the authors use this effect to develop a fiber-based wavelength-measurement technique with high resolution