Linear ResponseΒΆ

  • Polarizability

    @jobs
    task: response
    @end
    
    @method settings
    basis: aug-cc-pvdz
    @end
    
    @response
    property: polarizability
    frequencies: 0-0.25 (0.05)
    @end
    
    @molecule
    charge: 0
    multiplicity: 1
    units: au
    xyz:  
    O   0.0   0.0   0.0
    H   0.0   1.4   1.1
    H   0.0  -1.4   1.1
    @end 
    
  • UV-Vis absorption spectrum calculation using random phase approximation (RPA)

    @jobs
    task: response
    @end
    
    @method settings
    basis: aug-cc-pvdz
    @end
    
    @response
    property: absorption
    nstates: 3
    @end
    
    @molecule
    charge: 0
    multiplicity: 1
    units: au
    xyz:  
    O   0.0   0.0   0.0
    H   0.0   1.4   1.1
    H   0.0  -1.4   1.1
    @end 
    
  • Linear absorption cross-section calculation using complex polarization propagator (CPP)

    @jobs
    task: response
    @end
    
    @method settings
    basis: aug-cc-pvdz
    @end
    
    @response
    property: absorption (cpp)
    frequencies: 0-0.25 (0.05)
    @end
    
    @molecule
    charge: 0
    multiplicity: 1
    units: au
    xyz:  
    O   0.0   0.0   0.0
    H   0.0   1.4   1.1
    H   0.0  -1.4   1.1
    @end 
    
  • Linear response with pulsed external field: Correction to time-domain dipole moment

    The current version of VeloxChem allows for calculation of the linear electric dipole response for the frequency region of a single Gaussian-envelope pulse deemed sufficiently large (using the @pulses module). The time-domain shape parameters for this pulse may be specified by the user, optionally storing a collection of pertinent results in an HDF5-formatted file or a plaintext ASCII file whose name may be specified by the user. An example of an input file that when run will carry out such a calculation is given below. For more documentation about the available keywords, please consult the source file whose path from the VeloxChem root folder is src/pymodule/pulsedrsp.py. Note in particular that the default of carrier envelope phase may need adjustment to match your desired setup.

    Sample input:

    @jobs
    task: hf
    @end
    
    @method settings
    basis: aug-cc-pvdz
    @end
    
    @molecule
    charge: 0
    multiplicity: 1
    units: au
    xyz:
    O   0.0   0.0   0.0
    H   0.0   1.4   1.1
    H   0.0  -1.4   1.1
    @end
    
    @pulses
    envelope: gaussian
    field_max : 1.0e-5
    number_pulses: 1
    centers: 300 
    field_cutoff_ratio: 1e-5
    frequency_range : 0.2-0.4(0.001)
    carrier_frequencies: 0.325
    pulse_widths: 50 
    pol_dir: xyz
    h5 : pulsed
    ascii : pulsed
    @end
    

    If HDF5-formatted data was produced during this calculation, that data may used for plot generation using the script located at utils/pulsed_response_plot.py from the VeloxChem root folder. Please note that Python version 3 is required to run this script. Please also note that other standard python modules such as matplotlib must be installed on the system from which this script is run. The script will take the HDF5-formatted data produced during the VeloxChem calculation and generate a plot of the real and imaginary frequency-domain electric dipole polarizability, a representation of the perturbing field in the frequency domain, the resulting (real-valued) first-order dipole moment correction in the time domain and a representation of the perturbing field in the time domain. For more information and further description of how to run this script, please consult the documentation written inside it.