Can I only run the freq job and only using Qchem as my ESS?

[NtuCheRoy]

I want to run a simple job, using Qchem to analyze hydrogen with b3lyp/6-31g* level of theory. I have set up my yml file with below code.

job_types:
    freq: true

However, the output file shows that ARC turns out to run the opt, conformers, sp, 1d_rotors, freq and fine job together. My first question is that can I only run freq job? Below is the message from output file. And my server only has Qchem as ESS. I watch the arc/settings.py file, and in the 84 line it show that level_ess is the default that level and basis set relating to specific ESS. If I want to use Qchem to analyze some molecules with b3lyp/6-31g* level of theory. It seems that I have to set up the level_ess. Otherwise, it would have KeyError: 'gaussian'. I try to set up the level_ess by type below code in my yml file, but still have KeyError: 'gaussian'. Could you tell me how to run job by only using Qchem as ESS?

levels_ess:
    qchem:
    - b3lyp

[alongd]

To run a single job type, you need to specify all other job types as False in under job_types:

job_types:
    conformers: false
    opt: false
    fine_grid: false
    freq: true
    1d_rotors: false
    sp: false

Soon, this will not be necessary (once #186 is merged) and a user will be able to request this behaviour via the specific_job_type argument. Note that if your species is only represented in the input file using SMILES and does not have a 3D xyz geometry, conformers will be spawned, and perhaps opt as well.

Regarding your second question: To direct ARC to use QChem for a certain level of theory, you should modify the levels_ess dictionary in the settings.py file, it's not a part of the input file. Use, for example:

levels_ess = {
    'gaussian': ['apfd', 'm062x'],
    'molpro': ['ccsd', 'cisd', 'vpz'],
    'qchem': ['b3lyp']
}

[NtuCheRoy]

I type below code in my yml file. However, in my output file it seems that ARC still run not only freq job.

project: arc_demo_1

ess_settings:
        qchem:
                - local

job_types:
        conformers: false
        opt: false
        fine: false
        freq: true
        sp: false
        1d_rotors: false
        orbitals: false
        lennard_jones: false
        bde: false

level_of_theory: b3lyp/6-31g*
conformer_level: b3lyp/6-31g*
scan_level: b3lyp/6-31g*
ts_guess_level: b3lyp/6-31g*

species:
  - label: hydrogen
    xyz: |
            H         -4.12347       -0.08887        0.00000
            H         -3.70381        0.48134        0.00000

[alongd]

That's OK, ARC reports on the levels it uses for these job types, but I think that with your current settings it will not actually spawn them. Let me know if you find otherwise.