Twister: construction and structural relaxation of commensurate moiré superlattices

Abstract Introduction of a twist between layers of two-dimensional materials which leads to the formation of a moire pattern is an emerging pathway to tune the electronic, vibrational and optical properties. The fascinating properties of these systems is often linked to large-scale structural reconstruction of the moire pattern. Hence, an essential first step in the theoretical study of these systems is the construction and structural relaxation of the atoms in the moire superlattice. We present the Twister package, a collection of tools that constructs commensurate superlattices for any combination of 2D materials and also helps perform structural relaxations of the moire superlattice. Twister constructs commensurate moire superlattices using the coincidence lattice method and provides an interface to perform structural relaxations using classical forcefields. Program summary Program Title: Twister CPC Library link to program files: https://doi.org/10.17632/frfrj8wpbk.1 Developer's repository link: https://github.com/qtm-iisc/Twister Licensing provisions: BSD 3-clause Programming language: Python External routines/libraries: numpy, scipy, mpi4py, matplotlib Nature of problem: Moire patterns can be constructed from 2D materials by twisting the layers with respect to each other. Simulation of these patterns using forcefields or density functional theory requires the construction of periodically repeating moire superlattices. Solution method: Moire superlattices are constructed using the coincidence site lattice theory while also allowing the user to accomodate strains in the layer. Twister also helps perform structural relaxation of the moire superlattice using forcefields by interfacing to the LAMMPS package.