CONAN─Novel Tool to Create and Analyze Liquids in Confined Space

Abstract

Modeling of complex liquids at solid surfaces and in confinement is gaining attention due to an increase in computer power and advancement of simulation techniques. Therefore, tools to set up structures and for analysis are needed. In this paper, we present CONANa Python code designed to facilitate the study of liquids interacting with solid structures, such as walls or pores. Among other things, the program provides the option to generate a variety of different structures, including carbon walls and nanotubes and their boron nitride analogs, as well as the ability to analyze various structural properties of confined and interfacial liquids. In the case of the ionic liquid 1-butyl-3-methylimidazolium acetate in carbon nanotubes of different sizes, we demonstrate the abilities of our tool. The average density within the confinement highly depends on the carbon nanotube size, and it is generally lower than the density of the bulk liquid. The arrangement of the individual species within the tube also depends on size, with radial layers forming within the tubular confinement. The density is largely increased in the respective layers, while it is drastically reduced between the layers.

Coordination Behavior of a Confined Ionic Liquid in Carbon Nanotubes from Molecular Dynamics Simulations

“…This is also supported by the mass density profiles of the cation, see Figure , where the carbon atoms in the ring and the alkyl groups show well-defined maxima. A similar behavior was found in an earlier study of the IL [C 4 C 1 Im]­[OAc] in a (12,0) CNT …”

“…Because charge scaling usually affects the dynamical behavior more than the structural one, we implemented the option to analyze the velocity of species in the pore structures into CONAN in the form of radial velocity distributions. Similarly, as for the radial density profiles, the space around the center axis of the pore is divided into distinct radial increments. The velocity of each atom within the pore is calculated and sorted into the according increments.…”

“…New tools are helpful to analyze such anisotropic liquid–solid-systems. CONAN, − a program developed by our group that allows the generation of carbon structures, the setup of the simulation box, and the analysis of the simulation trajectory data, was created for this purpose. Besides the established analysis methods from our previous publication, new features have been added to the code to analyze the coordination and velocity of ions in the liquid with respect to their distance from the solid structure.…”

“…Each system consists of a bulk phase containing 512 ion pairs and a carbon pore structure generated using CONAN. 48 The structures are pristine and consist of a CNT with a radius in the nanometer regime and carbon walls attached to both open ends. The studied pores were constructed with CNTs in an armchair configuration of three different sizes.…”

“…A similar behavior was found in an earlier study of the IL [C 4 C 1 Im]-[OAc] in a (12,0) CNT. 48 In contrast, the ions within the pore of system N 10 form a tubular void around the central axis. The cations occupy one specific radial position at 0.5 d rad /r CNT , while the anions can be found in two different radial positions (0.2 d rad /r CNT and 0.5 d rad /r CNT ).…”