aiida-vibroscopy

aiida-vibroscopy

vibroscopy.fp

vibroscopy.vibrational

vibroscopy.dielectric

Workchain computing different second and third order tensors. It computes the high frequency dielectric tensor, the Born effective charges, the non-linear optical susceptibility and Raman tensors using homogeneous small electric fields via the electric enthalpy functional.

vibroscopy.dielectric.numerical_derivatives

Workchain carrying out numerical derivatives. It computes the first and second order derivatives of forces and polarization in respect to electric field, to obtain dielectric tensor, Born effective charges, non linear optical susceptibility and Raman tensors. Forces and polarization must be passed as TrajectoryData as a dictionary in `data`. Numerical derivatives can have different number of evaluation points, depending on order and accuracy. The price to pay is the standardization of the structure of the dictionary to pass to this namespace. To understand, let's review the approach.In central differencs approach we need the evaluation of the function at the value we want the derivative (in our case at :math:`\\mathcal{E}=0`, E is the electric field), and at displaced positions from this value. The evaluation of the function at these points will have weights (or coefficients), which depend on order and accuracy. For example: - :math:`\\frac{df}{dx} = \\frac{ 0.5 \\cdot f(+1.0 \\cdot h) -0.5 \\cdot f(-1.0 \\cdot h) }{h} +\\mathcal{O}(h^2)` - :math:`\\frac{d^2 f}{dx^2} = \\frac{ 1.0 \\cdot f(+1.0 \\cdot h) -2.0 \\cdot f(0. \\cdot h) +1.0 \\cdot f(-1.0 \\cdot h) }{h^2} +\\mathcal{O}(h^2)` Referring to the coefficients for each step as :math:`c_i`, where `i` is an integer, our convention is to put in sequence the Trajectory data with increasing numbers as labels, for example: | '0': TrajectoryData for :math:`c_1`, | '1': TrajectoryData for :math:`c_{-1}`, | '2': TrajectoryData for :math:`c_2`, | '3': TrajectoryData for :math:`c_{-2}`, | ... This way to creating an analogous of an array with coefficients :math:`[c_1,c_{-1},c_2,c_{-2}, \\dots]`. These dictionaries are going to be put as sub-dictionary in a general `data` dictionary. Each sub-dict has to be put with a key with suffix a number indicating which tensor component is referring to. In our case, we use a similar Voigt notation. Namely we have two cases: * first order derivatives: keys suffices are 0,1,2; 0 for :math:`[i,x]`, 1 for :math:`[i,y]`, 2 for :math:`[i,z]` (with :math:`i={x,y,z}`) * second order derivatives: keys suffices are 0,...5; 0 for :math:`[i,x,x]`, :math:`\dots` (as in Voigt), 5 for :math:`[i,x,y]` (with :math:`i={x,y,z}`) The prefix can be anything. Best practice is using ``field_`` with and underscorre as prefix. The Trajectory data for the :math:`c_0` coefficient (i.e. the one with :math:`\mathcal{E}=0`) must be passed with a different key, namely ``null_field``. This is to avoid errors and due to the fact that is common to the all derivatives.

vibroscopy.phonons.harmonic

Workchain for frozen phonons calculations. Non-analytical constants (NAC) and higher order mixed derivatives are computed via finite differences through finite electric fields. See :class:`~aiida_vibroscopy.workflows.DielectricWorkChain` for more details on how they are carried out.

vibroscopy.phonons.phonon

Class for computing force constants of phonons, without non-analytical corrections.

vibroscopy.spectra.intensities_average

Workchain that computes IR and Raman spatial and q-direction average spectra.

vibroscopy.spectra.iraman

Workchain for automatically compute IR and Raman spectra using finite displacements and fields. For other details of the sub-workchains used, see also: * :class:`~aiida_vibroscopy.workflows.dielectric.base.DielectricWorkChain` for finite fields * :class:`~aiida_vibroscopy.workflows.phonons.base.PhononWorkChain` for finite displacements