parameters section

The parameters section defines additional physical and numerical parameters for atomistic models for nanoplasmonics (\(omegatext{FQ}\) and \(omegatext{FQF}\mu\) ).

This section is optional, and must be omitted if you want to rely entirely on default parameters [currently defined for: sodium, carbon, silver, gold].

Each atom type is given as a key, and parameters are defined in nested blocks (see Example)

Valid keywords

Keyword	Type	Allowed Values	Default
tau	float or string	> 0.0	units: a.u.
sigma0	float or string	> 0.0	units: S/m
w_p	float or string	> 0.0	units: eV
gamma	float or string	> 0.0	units: a.u.
scaling sigma0-tau	float or string	> 0.0	–
a_ij	float or string	> 0.0	units: a.u.
fermi_function.d	float or string	> 0.0	–
fermi_function.s	float or string	> 0.0	–
fermi energy	float or string	> 0.0	units: eV
wfqfmu file	string	valid path to .csv	–
permittivity	string	silver etchegoin, gold etchegoin	–

Notes

• Each atom type used in the input_geometry must have a corresponding entry here, unless default values are exploited.

• Each atom type defined in input_geometry can define its own parameters block.

• tau : Electron relaxation/scattering time (Drude model). tau can be expressed in:

  • a.u. or au

  • s

  • fs

• sigma0 : Static electrical conductivity (Drude model). sigma0 can be expressed in:

  • s/m

  • a.u. or au

• w_p : Plasma frequency (Drude model). w_p can be expressed in:

  • eV

  • nm

  • micron or um

  • cm-1 or cm^-1

  • thz

  • a.u. or au

• gamma : Drude damping constant. gamma can be expressed in:

  • au or a.u.

  • fs^-1 or fs-1

  • s^-1 or s-1

• To define the Drude part of the response, any combination between (sigma0, w_p) and (tau, gamma) must be provided.

• scaling sigma0-tau : Scaling factor applied to both sigma0 and tau, used to adjust the conductivity model for specific materials (e.g. sodium for which fefault: 10)

• a_ij: effective area between the atoms. a_ij can be expressed in:

  • au or a.u.

  • nm^2 or nm2

  • ang^2 or ang2 or angstrom^2 or angstrom2

• fermi function: defines the Fermi-like function parameters for tunneling regime.

  • fermi_function.d: damping width

  • fermi_function.s: damping slope

• fermi energy : Fermi energy. Used only for graphene-based materials

• wfqfmu file : points to a CSV file with frequency-dependent parameters. The file must contains 3 columns: frequencies (eV) Re(alpha) Im(alpha)

• permittivity refers to a predefined dielectric function, from which the interband polarizability is computed.

• When more than one atom type is defined in the input_geometry, it is possible to define interaction-specific damping functions using the interaction AtomA->AtomB syntax (see Example).

  This subsection is optional, and must be omitted if you want to rely entirely on default parameters [currently defined for: silver-gold bimetallic systems].

  Keyword	Type	Description
  fermi_function.d	float or string	Width of the damping function
  fermi_function.s	float or string	Slope of the damping function

Example

parameters:
  Au:
    tau: 318.018
    sigma0: 11834849.81
    A_ij: 9.61
    fermi_function:
      d: 12.0
      s: 1.1
    wfqfmu file: jc_gold_polar.csv
  Ag:
    tau: 1633.608
    sigma0: 65313000.0
    A_ij: 9.61
    fermi_function:
      d: 12.0
      s: 1.1
    wfqfmu file: jc_silver_polar.csv
  interaction Au->Ag:
    fermi_function:
      d: 12.0
      s: 0.82555
  interaction Ag->Au:
    fermi_function:
      d: 12.0
      s: 0.82555