These appendices consist of optional exercises, and are mentioned in earlier parts of the tutorial. Go through them only if you have time.

# 11. Calculation input validation¶

This appendix shows additional ways to debug errors with Quantum ESPRESSO, namely how to take advantage of a powerful tool to validate the input to Quantum ESPRESSO and possibly suggest the correct name to misspelled keywords.

There are various reasons why you might end up providing a wrong input to a Quantum ESPRESSO calculation. Let’s check for example this input dictionary, where we inserted two mistakes:

parameters_dict = {
'CTRL': {
'calculation': 'scf',
'restart_mode': 'from_scratch',
},
'SYSTEM': {
'nat': 2,
'ecutwfc': 30.,
'ecutrho': 200.,
},
'ELECTRONS': {
'conv_thr': 1.e-6,
}
}


The two mistakes in the dictionary are the following:

• We wrote a wrong namelist name (CTRL instead of CONTROL).

• We inserted the number of atoms explicitly: while that is indeed how the number of atoms is specified in Quantum ESPRESSO, in AiiDA this key is reserved by the system, since this information is already contained within the StructureData.

After we correct the dictionary parameters_dict, we could run the calculation directly. Alternatively, we can use a tool of the the aiida-quantumespresso plugin, the ‘input helper’, which checks the inputs before submitting the calculation.

In your script, after you define parameters_dict, you can validate it with the following command (note that you need to pass also an input crystal structure, structure, to allow the validator to perform all the needed checks):

PwCalculation = CalculationFactory('quantumespresso.pw')
validated_dict = PwCalculation.input_helper(parameters_dict, structure=structure)
parameters = Dict(dict=validated_dict)


The input_helper method will check for the correctness of the input parameters. If misspelling or incorrect keys are detected, the method raises an exception, which stops the script before submitting the calculation and thus allows for a more effective debugging.

With this utility, you can also provide a list of keys, without providing the namelists (useful if you don’t remember where to put some variables in the input file). Hence, you can provide to input_helper a dictionary like this one:

parameters_dict = {
'calculation': 'scf',
'tstress': True,
'tprnfor': True,
'ecutwfc': 30.,
'ecutrho': 200.,
'conv_thr': 1.e-6,
}

validated_dict = PwCalculation.input_helper(
parameters_dict,
structure=structure,
flat_mode=True
)


If you print validated_dict, it will look like the following:

{
'CONTROL': {
'calculation': 'scf',
'tstress': True,
'tprnfor': True,
},
'SYSTEM': {
'ecutwfc': 30.,
'ecutrho': 200.,
},
'ELECTRONS': {
'conv_thr': 1.e-6,
}
}