Quantum point defects in 2D materials: The QPOD database

Abstract

Atomically thin two-dimensional (2D) materials are ideal host systems for quantum defects as they offer easier characterisation, manipulation and read-out of defect states as compared to their bulk counterparts. Here we introduce the Quantum Point Defect (QPOD) database with more than 1900 defect systems comprising various charge states of 503 intrinsic point defects (vacancies and antisites) in 82 different 2D semiconductors and insulators. The Atomic Simulation Recipes (ASR) workflow framework was used to perform density functional theory (DFT) calculations of defect formation energies, charge transition levels, Fermi level positions, equilibrium defect and carrier concentrations, transition dipole moments, hyperfine coupling, and zero-field splitting. Excited states and photoluminescence spectra were calculated for selected high-spin defects. In this paper we describe the calculations and workflow behind the QPOD database, present an overview of its content, and discuss some general trends and correlations in the data. We analyse the degree of defect tolerance as well as intrinsic dopability of the host materials and identify promising defects for quantum technological applications. The database is freely available and can be browsed via a web-app interlinked with the Computational 2D Materials Database (C2DB).

Toward machine learning for microscopic mechanisms: A formula search for crystal structure stability based on atomic properties

“…In recent years, the continuous growth of available computational power 1 has stimulated scientists to move in the direction of high-throughput simulations. [2][3][4][5][6][7][8][9][10] Along this line, open access databases, such as OQMD, 11,12 NOMAD, 13,14 Aflowlib, 15 C2DB, 16,17 QPOD, 18 Materials Project, 19 Materials Cloud, 20 and related AiiDA, 21,22 provide researchers with a huge collection of basic first-principles results. A large amount of ab initio data is thus available, which can be used for deeper analyses and studies, provided one can count on proper tools to extract relevant information out of them.…”