Peng: A program for transport properties of low-density binary gas mixtures

Abstract

The fundamental properties of molecules bridge experiment and theory. Transport properties (diffusion, thermal diffusion, thermal conductivity and viscosity) of binary mixtures are measurable in experiments, and well-defined in theory, but difficult to compute with high accuracy. In addition to high-accuracy inter-molecular potential energy curves (PECs), a reliable and high-order solution program that compute the properties based on the PECs is required. In this work, we present a computer program called Peng that performs the collision integration numerically, and solves the Boltzmann equation in Chapman–Enskog fashion. The program has been devised to perform both parts of the solution procedure to arbitrary order, so that no hard-coded limitation will prevent a user from computing at higher precision, except the amount of RAM and the required computational time. Peng is well-designed in an Object-Oriented Programming (OOP) fashion, which make the program clear and easy to modify. In addition to the end-user oriented program, Peng is also compiled as a dynamic shared library that may readily be extended and embedded in users' programs. Program summaryProgram Title:PengCPC Library link to program files:https://doi.org/10.17632/n5tm9426jx.1Developer's repository link:https://github.com/zhaiyusci/pengCode Ocean capsule:https://codeocean.com/capsule/9951686Licensing provisions: LGPLProgramming language: C++Nature of problem: Nowadays, quantum chemistry provides high-accuracy intermolecular interactions potential energy curves (PECs), and more and more accurate thermophysical properties of dilute gases can be measured experimentally. It is meaningful to build a bridge between thermophysical properties and PECs, so that people can refine the PECs and learn more about the nature of dynamics of gases. For a dilute binary gas mixture, the theory, the Boltzmann equation, and its solution has been available for a long time, but fewer numerical solution packages are available for the public. An easy-to-use and easy-to-extend software package is required.Solution method: To complete the work, we have created a program that computes the collision integrals (Ω(ℓ,s)) for a set of temperatures, following which the thermophysical properties are computed using the Chapman–Enskog solutions of the Boltzmann equation. Both parts of the program are written in C++. The program is easy to use, and a well-designed framework is provided thanks to the Object-oriented design. Users with programming experience can readily extend the present work.Additional comments including restrictions and unusual features: In this version, the program is limited to the computation of the properties of mixtures of structureless atoms. For polyatomic molecules, additional work need to be done.