Materials databases, high throughput computing, and data mining has emerged as powerful tools for screening and rapid prototyping of functional materials. Quantum magnetic systems, with often competing ground states and phases, are a challenge for ab initio modelling. In recent work at Nordita and KTH an important step forward was taken for predictive modeling of the properties of magnetic solids. Such database will be an important tool for users of both ESS and MAX IV working in the field of organic and/or magnetic materials.
A framework has been developed for high throughput calculations of dynamical magnetic properties, using as input only the crystallographic structures of the materials. By means of this technique a data set for crystalline organic magnets has been produced containing for each system predictions of the local magnetic moments (spins), the strength of the pairwise magnetic interactions, the ground state pattern of the magnetization, and the characteristics of the dynamics of the interacting spins. The new dataset has been stored in the Organic Materials Database (OMDB) (https://omdb.mathub.io/), a platform for virtual material science experiments. In combination with advanced pattern matching algorithms, the data enables an OMDB user to query for materials with desired properties. An important use case is for a researcher to mine for materials to synthesize and characterize with in-house resources, and also for later consideration in experiments at large-scale facilities including neutron scattering instruments.
Figure: (a) shows the crystallographic structure of the collinear antiferromagnetic hexaiso-propylnickelocene C28H46Ni, with the magnetic sites and ground state spin configuration shown as red arrows. (b) shows the calculated T = 0 K magnon dispersion (black dashed line) and the T = 1 K dynamical structure factor S(q,). The latter could be experimentally measured by inelastic neutron scattering (INS). Figures reprinted with permission from J. Hellsvik et al., Phys. Rev. Materials 4, 024409 (2020). Copyright 2020 by the American Physical Society.
The Organic Materials Database (OMDB) is developed and maintained in the group of Prof. Alexander Balatsky at Nordita. Work on magnetic excitation spectra on the OMDB is an activity within the Swedish Quest for BIFROST, a collaboration lead by Assoc. Prof. Martin Månsson at KTH, aiming at early use of the BIFROST spectrometer at the European Spallation Source (ESS).
Further information: Johan Hellsvik, Roberto Díaz Pérez, R. Matthias Geilhufe, Martin Månsson, Alexander V. Balatsky, Phys. Rev. Materials 4, 024409 (2020)
A high-throughput database of magnetic properties of organometallic materials opens the path towards establishing general concepts of materials statistics. The method can be naturally extended to include other interactions such as Dzyaloshinskii-Moriya interaction, Ising interaction, and single-site magnetocrystalline anisotropy energy to the magnetic Hamiltonian, of relevance for the low-energy excitation spectra of quantum organometallic materials.