MCPlas, a MATLAB toolbox for reproducible plasma modelling with COMSOL

The MCPlas toolbox represents a collection of MATLAB functions for the automated generation of an equation-based fluid-Poisson model for non-thermal plasmas in the multiphysics simulation software COMSOL. Following the development of the new generation of the LXCat platform, all input data are prepared in a structured and interoperable JSON format and can be supplied and validated using existing JSON schemas. The toolbox includes fully transparent, editable MATLAB source code and offers an advanced description of electron transport in addition to commonly used approaches in the plasma modelling community. It supports one-dimensional and two-dimensional modelling geometries employing Cartesian, polar and cylindrical coordinate systems. MCPlas is tested on two reference cases: DC- and RF-driven low-pressure glow discharges in argon. Comparison of MCPlas results with results obtained by employing COMSOL's Plasma Module verifies the reliability of the plasma model implemented by MCPlas and demonstrates the significance of electron transport treatment and boundary conditions applied in the toolbox. Using the same examples, the easy handling of complex reaction kinetic models in MCPlas and the reusability of its JSON input data across different modelling platforms are illustrated. This demonstrates that MCPlas provides a transparent and reproducible workflow for the simulation of non-thermal plasmas using COMSOL. PROGRAM SUMMARY Program title: MCPlas CPC Library link to program files: (to be added by Technical Editor) Developer's repository link: ( https://github.com/INP-SDT/MCPlas ) Code Ocean capsule: (to be added by Technical Editor) Licensing provisions: MIT Programming language: MATLAB Nature of problem: {Fluid-Poisson simulations of low-temperature plasmas are widely used but often lack reproducibility, transparency and interoperability. In most commercial and in-house tools, the governing equations, boundary conditions and reaction kinetics are hidden in proprietary project files or ad hoc scripts, and complex reaction kinetics models (RKMs) must be entered manually. Moreover, there is no machine-readable community standard or format for plasma chemistries and related input data, so the same RKM cannot be reliably reused across different modelling platforms. As a result, the precise reconstruction and verification of published models is difficult, comparison between tools is hindered, and the same chemistry cannot be reliably reused across different codes, conflicting with the FAIR (Findable, Accessible, Interoperable, Reusable) data principles.} Solution method: {MCPlas addresses these issues by standardising all input data and automating the implementation of a fluid-Poisson model for non-thermal plasmas in COMSOL. All model-defining information, such as species states and properties, RKM, transport and rate coefficients, model setup and numerical parameters, is stored in structured JSON documents. These are validated against JSON schemas aligned with the new LXCat data model and the plasma metadata schema Plasma‑MDS. From these schema-validated JSON files, MCPlas automatically builds fully equation-based fluid-Poisson models in COMSOL via the LiveLink{} for MATLAB{{4}{4}} module, with explicit access to the implemented equations and boundary conditions. The toolbox offers options for advanced electron transport description and boundary treatments in addition to commonly used formulations. The same JSON-based model definitions can be used unchanged in other software packages for plasma modelling, enabling interoperable, cross-platform simulations and implementing a transparent, FAIR-compliant workflow for reproducible plasma modelling.} Additional comments including restrictions and unusual features: The commercial software packages MATLAB44 (R2023a), COMSOL Multiphysics44 (v.6.2) and the COMSOL module LiveLink for MATLAB44 were used for development MCPlas and testing generated models. There should be no restrictions on using MCPlas with other software versions.