Keywords: user_guide

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## 3.2 Data files

The output data files are written in the directory `outdir/prefix.save`, as specified in variable `prefix` (a string that is prepended to all file names, whose default value is `prefix='pwscf'`). `outdir` is specified via environment variable `ESPRESSO_TMPDIR`. The usage of variable `outdir` is still possible but deprecated. The `FoX` library is used to write a ``head'' data file in a XML format. This file has a ``schema'' that can be found on `http://www.quantum-espresso.org/ns/qes/qes-1.0`.

In case of multi-step calculations such as: `'md', 'relax', 'vc-md ', 'vc-relax'` the XML files contains also elements reporting the intermediate configurations. By default includes a maximum of 250 intermediate elements uniformly distributed along the trajectory and including first and last step. If one want to change the maximum number of intermediate steps described in the XML file it is sufficient to set the `MAX_XML_STEPS` variable to the desired value.

For more information about the XML file contents see the Developer Manual. The data directory contains binary files that are not guaranteed to be readable on different machines. If you need file portability, compile the code with HDF5 (see the general User Guide).

The execution stops if you create an ``EXIT'' file `prefix.EXIT` either in the working directory (i.e. where the program is executed), or in the `outdir` directory. Note that with some versions of MPI, the working directory is the directory where the executable is! The advantage of this procedure is that all files are properly closed, whereas just killing the process may leave data and output files in an unusable state. If you start the execution with the EXIT file already in place, the code will stop after initialization. Alternatively: set `nstep` to 0 in input. This is useful to have a quick check of the correctness of the input.

Next: 3.3 Electronic structure calculations Up: 3 Using PWscf Previous: 3.1 Input data Contents