(1e) How to Use the Atomistic Monte Carlo Package Cassandra: Liquid Phase Properties and Vapor-Liquid Phase Equilibria

Cassandra is an open source atomistic Monte Carlo simulation package that is used by over 300 researchers worldwide. Cassandra is capable of simulating any number of molecules composed of rings, chains, or both. It can be used it to simulate small organic molecules, oligomers, and ionic liquids. It handles a standard "Class I"-type force field having fixed bond lengths, harmonic bond angles and improper angles, a CHARMM or OPLS-style dihedral potential, a Lennard-Jones 12-6 potential or Mie potential and fixed partial charges. Cassandra can simulate the following ensembles: canonical (NVT), isothermal-isobaric (NPT), grand (muVT), osmotic (muPT), and Gibbs (NVT and NPT versions).

In this brief hands-on tutorial, we will cover the essentials of how Cassandra works and the types of properties is can compute. We will provide step-by-step instructions for creating input files, how to interpret the output from Cassandra and how to avoid common mistakes. At the end of this tutorial, users will be able to simulate a pure liquid phase at constant pressure and temperature as well as vapor-liquid equilibria using the Gibbs ensemble. Extensions to more complex systems will be discussed if time permits.

Who should attend: undergraduate students, graduate students or other researchers who are new to molecular simulation and are interested in learning how to carry out Monte Carlo simulations of fluids.