PARPHOM: PARallel PHOnon calculator for Moiré systems

S Mandal and I Maity and HR Krishnamurthy and M Jain, COMPUTER PHYSICS COMMUNICATIONS, 316, 109760 (2025).

DOI: 10.1016/j.cpc.2025.109760

The introduction of a twist between two layers of two-dimensional materials has opened up a new and exciting field of research known as twistronics. In these systems, the phonon dispersions show significant renormalization and enhanced electron-phonon interactions as a function of the twist angle. However, the large system size of the resulting moir & eacute; patterns in these systems makes phonon calculations computationally challenging. In this paper, we present PARPHOM, a powerful code package designed to address these challenges. PARPHOM enables the generation of force constants, computation of phononic band structures, and determination of density of states in twisted 2D material systems. Moreover, PARPHOM provides essential routines to investigate the finite temperature dynamics in these systems and analyze the chirality of the phonon bands. This paper serves as an introduction to PARPHOM, highlighting its capabilities and demonstrating its utility in unraveling the intricate phononic properties of twisted 2D materials. Program summary Program Title: PARPHOM CPC Library link to program files: https://doi.org/10.17632/gp6rzrp47m.1 Developer's repository link: https://github.com/qtm-iisc/PARPHOM Licensing provisions: GNU General Public License v3.0 Programming language: FORTRAN, Python External Routines/libraries: numpy, LAMMPS (serial Python wrapper), mpi4py, ScaLAPACK, HDF5, matplotlib, scipy, Spglib Nature of problem: Due to the large number of atoms in 2D moir & eacute; systems, performing phonon calculations is quite challenging. The exorbitantly high memory requirements of such calculations make them infeasible with currently available codes. Solution method: A parallel algorithm to generate the force constant matrices for these large moir & eacute; systems has been implemented. Parallel diagonalization routines available in ScaLAPACK are then used to diagonalize the dynamical matrices constructed from the force constants at each q points.

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