How to run Express from command line

To carry out a computation, first, users need to prepare the input files introduced in section "Configuration files". Then if the xps command is installed, run in terminal:

xps run eos.toml  # equation of state workflow
xps run vdos.toml  # phonon workflow
xps run qha.toml  # QHA workflow

As explained in "Configuration files", the file name (eos.toml, etc.) of the configuration file does not matter. It is the recipe field that determines the type of workflow.

It is often suggested to put the above commands in a script file with a header and submit it to a workload manager like Slurm. However, users can also request an interactive session and run code Julia REPL.

julia> using Express.EquationOfStateWorkflow.Recipes

julia> using QuantumESPRESSOExpress

julia> workflow = buildworkflow("eos.toml");

julia> run!(workflow);

For phonon and the QHA workflow, run using Express.PhononWorkflow.Recipes and using Express.QuasiHarmonicApproxWorkflow.Recipes in the first step.

In an EOS workflow, the final results include outputs returned by Quantum ESPRESSO, a list of raw data (volume-energy pairs), and a fitted EOS. If something goes wrong, the workflow might be terminated. The state of the workflow (i.e., the status of each job) and errors will be saved in a file for debugging. Once the bug is fixed, run xps run <path-to-config-file> again, and express will retry the failed jobs. To print either input or output data in a formatted, readable form, run

xps print <file-name>

where the allowed extensions of <file-name> are .jld2, .json, .yaml or .yml, and .toml. The last four extensions correspond to three human-readable data-serialization file formats, i.e., JSON, YAML, and TOML, while .jld2 is a binary serialization format only recognizable to Julia. For example,

xps print eos.toml
xps print raw.json
xps print eos.jld2

express can also plot some data, such as the fitted EOS applied to a certain range of volumes along with the raw data. The corresponding command is

xps plot <file-name>

where <file-name> refers to the EOS binary file with extension .jld2.

These are the three most important commands of express. These catchy commands cover all the functionalities we have promised, including but not limited to unit conversion, pseudopotential downloading, input validation and generation, calculation monitoring, task distribution, gathering and analysis of results, error handling, logging, and visualization. We hope they can facilitate tedious work as much as possible.