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AiiDA, the high-throughput environment, is built in a modular fashion. This makes it possible to support any other simulation code via plugins that go from the management of single runs to sophisticated workflows for the computation of advanced materials properties.
AiiDA has plugins for over 30 simulation packages and the list is growing also thanks to external contributors. The full list of currently supported codes can be found on the official AiiDA plugin registry, including links to the plugin code repositories and their documentation. In particular, MAX implements and supports the AiiDA plugins for all MAX flagship codes.
Quantum ESPRESSO, one of the MAX flagship codes, is a popular and powerful DFT simulation code. The aiida-quantumespresso package provides not only plugins to make sure that all codes of Quantum ESPRESSO can be used with AiiDA (including pw.x, cp.x, neb.x, ph.x, and most of the post-processing tools), but also a number of powerful automated workflows.
The workflows of the aiida-quantumespresso package, centered around the pw.x code of 4 the Quantum ESPRESSO suite, underwent a lot of development. The main goal was to develop a workflow, the PwWorkChain, that can compute the relaxed ground-state of any crystal structure without any further user inputs. This workflow could be a powerful turn-key solution that can be used as the starting point for many other tools computing complex structural properties (see also discussion on common workflows at the end of this page).
The workflows and turn-key solutions built around the MAX flagship code SIESTA are collected in the python package aiida-siesta, already available in the MAX website and on GitHub. The first enhancement concerns the introduction of a new AiiDA workflow called EqOfStateFixedCellShape. It is a tool for the calculation of the equation of state of a solid. Density Functional Theory (DFT) calculations with the SIESTA code are performed at 7 equidistant volumes around a starting volume in order to obtain the energy (E) versus volume (V) data.
The new workflow introduced, the SiestaSTMWorkChain, is the turn-key solution to the problem of producing simulated STM images for a given structure. The workflow performs a SIESTA run (through the SiestaBaseWorkChain) in order to produce a file with the local density of states (LDOS) in an energy window. The workflow automatically processes the LDOS file (through the STMplugin distributed in aiida-siesta package) to produce STM images.
An overview on the workflows currently available within the aiida-fleur plugin package (v1.1.0) is shown in the figure below. The most basic workflows are the FleurBaseWorkChain and the SCF workflow to handle errors, restarts and the convergence of underlying calculations with the MaX flagship code FLEUR. All other workflows within aiida-fleur are higher-level workflows to calculate specific properties and they deploy these two basic workflows as sub-workflows.
While the FLEUR quantum engine makes progress in exascale simulations of large magnetic structures such as skyrmions and Bloch points, it is essential to come up with tools to point at crystal structures that are worth investigating by an exascale ab-initio calculation.
As a part of this work, a set of workflows for computation of magnetic properties was developed. First of all, the CreateMagneticFilm workflow is responsible for construction and relaxation of a structure, which represents a substrate with deposited magnetic material. The resulting structure is ready-to-be-used in the other magnetic workflows: MAE, DMI dispersion and Spin Spiral dispersion workflows automate the calculation of corresponding magnetic properties. The AiiDA provenance graph of a MAE workflow is on display in the figure below, showing an SCF run and a single FLEUR run with the FleurBaseWorkChain.
Plugin and workflows for CP2K (former MaX Code)
CP2K is a quantum chemistry and solid-state physics package for atomistic simulations that belongs to the MAX codes family. Thanks to the linear scaling DFT implementation CP2K can fairly easily deal with the structures containing thousands of atoms.
To empower AiiDA users with full access to the whole spectrum of tools available within the CP2K package a simple but flexible aiida-cp2k plugin has been developed. The aiida-cp2k package also provides two work chains named Cp2kBaseWorkChain and Cp2kMultiStageWorkChain. The first one is able to automatically fix generic problems such as wall time exceeding or node crash. The second work chain provides a simple interface to run several step simulations with a possibility to perform a stepwise enhancement of the convergence settings. If with the initial settings the convergence can’t be achieved, the work chain will automatically switch to more robust ones that are provided by the user. In case none of the settings could make it converge, the work chain will stop and report an error.
Plugin and workflows for BigDFT
BigDFT’s AiiDA plugin is being developed in the context of the second MAX project. The second version of the plugin, 0.2.0 aims at allowing integration of existing PyBigDFT’s operations in AiiDA workflows. The low level workchain is an instance of the BaseRestartWorkChain AiiDA concept, enabling simple error handling for common issues, such as an exceeded walltime, or errors in inputs, to be performed, and job restarting when possible.
Each of the simple workflows provided by the BigDFT plugin will provide wrapper input generators following the common API, for instance a BigDFTRelaxationInputsGenerator tool with a get_builder method to provide the user the basic input sets to run a relaxation computation without knowing internals of BigDFT workflows, and allowing integration in more generic workflows.