qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential

class HarmonicPotential(molecule)

Implements a 1D Harmonic potential.

Input units are Angstroms (distance between the two atoms), and output units are Hartrees (molecular energy).

Parameter

molecule (Molecule) – the underlying molecule.

Verursacht

ValueError – Only implemented for diatomic molecules

__init__(molecule)

Parameter

molecule (Molecule) – the underlying molecule.

Verursacht

ValueError – Only implemented for diatomic molecules

Methods

__init__(molecule)	type molecule Molecule
dissociation_energy([scaling])	Returns the estimated dissociation energy for the current fit.
eval(x)	After fitting the data to the fit function, predict the energy at a point x.
fit(xdata, ydata[, initial_vals, bounds_list])	Fits a potential to computed molecular energies.
fit_function(x, k, r_0, m_shift)	Functional form of the potential.
fundamental_frequency()	Returns the fundamental frequency for the current fit (in s^-1).
get_equilibrium_geometry([scaling])	Returns the interatomic distance corresponding to minimal energy.
get_maximum_trusted_level([n])	Returns the maximum energy level for which the particular implementation still provides a good approximation of reality.
get_minimal_energy([scaling])	Returns the smallest molecular energy for the current fit.
get_num_modes()	This (1D) potential represents a single vibrational mode
get_trust_region()	The potential will usually be well-defined (even if not useful) for arbitrary x so we return a fairly large interval here.
process_fit_data(xdata, ydata)	Mostly for internal use. Preprocesses the data passed to fit_to_data()
update_molecule(molecule)	Updates the underlying molecule.
vibrational_energy_level(n)	Returns the n-th vibrational energy level for the current fit (in Hartrees).
wave_number()	Returns the wave number for the current fit (in cm^-1).

dissociation_energy(scaling=1.0)

Returns the estimated dissociation energy for the current fit.

Parameter

scaling (float) – Scaling to change units. (Default is 1.0 for Hartrees)

Rückgabetyp

float

Rückgabe

estimated dissociation energy

eval(x)

After fitting the data to the fit function, predict the energy at a point x.

Parameter

x (float) – value to evaluate surface in

Rückgabetyp

float

Rückgabe

value of potential in point x

fit(xdata, ydata, initial_vals=None, bounds_list=None)

Fits a potential to computed molecular energies.

Parameter

• xdata (List[float]) – interatomic distance points (Angstroms)

• ydata (List[float]) – molecular energies (Hartrees)

• initial_vals (Optional[List[float]]) – Initial values for fit parameters. None for default. Order of parameters is k, r_0 and m_shift (see fit_function implementation)

• bounds_list (Optional[Tuple[List[float], List[float]]]) – Bounds for the fit parameters. None for default. Order of parameters is k, r_0 and m_shift (see fit_function implementation)

Rückgabetyp

None

static fit_function(x, k, r_0, m_shift)

Functional form of the potential.

Parameter

• x (float) – x parameter of harmonic potential functional form

• k (float) – k parameter of harmonic potential functional form

• r_0 (float) – r_0 parameter of harmonic potential functional form

• m_shift (float) – m parameter of harmonic potential functional form

Rückgabetyp

float

Rückgabe

harmonic potential functional form

fundamental_frequency()

Returns the fundamental frequency for the current fit (in s^-1).

Rückgabetyp

float

Rückgabe

fundamental frequency for the current fit

get_equilibrium_geometry(scaling=1.0)

Returns the interatomic distance corresponding to minimal energy.

Parameter

scaling (float) – Scaling to change units. (Default is 1.0 for Angstroms)

Rückgabetyp

float

Rückgabe

geometry corresponding to minimal energy

get_maximum_trusted_level(n=0)

Returns the maximum energy level for which the particular implementation still provides a good approximation of reality. Default value of 100. Redefined where needed (see e.g. Morse).

Parameter

n (int) – vibronic mode

Rückgabetyp

float

Rückgabe

maximum_trusted_level setted

get_minimal_energy(scaling=1.0)

Returns the smallest molecular energy for the current fit.

Parameter

scaling (float) – Scaling to change units. (Default is 1.0 for Hartrees)

Rückgabetyp

float

Rückgabe

smallest molecular energy for the current fit

get_num_modes()

This (1D) potential represents a single vibrational mode

Rückgabetyp

int

get_trust_region()

The potential will usually be well-defined (even if not useful) for arbitrary x so we return a fairly large interval here. Redefine in derived classes if needed.

Rückgabetyp

Tuple[float, float]

classmethod process_fit_data(xdata, ydata)

Mostly for internal use. Preprocesses the data passed to fit_to_data()

so that only the points around the minimum are fit (which gives more accurate vibrational modes).

Parameter

• xdata (List[float]) – xdata to be considered

• ydata (List[float]) – ydata to be considered

Rückgabetyp

Tuple[list, list]

Rückgabe

the processed data that fit better to a harmonic potential

update_molecule(molecule)

Updates the underlying molecule.

Parameter

molecule (Molecule) – chemistry molecule

Verursacht

ValueError – Only implemented for diatomic molecules

Rückgabetyp

Molecule

vibrational_energy_level(n)

Returns the n-th vibrational energy level for the current fit (in Hartrees).

Parameter

n (int) – vibrational mode

Rückgabetyp

float

Rückgabe

vibrational energy level for the current fit

wave_number()

Returns the wave number for the current fit (in cm^-1).

Rückgabetyp

int

Rückgabe

wave number for the current fit