262 lines
7.6 KiB
Plaintext
262 lines
7.6 KiB
Plaintext
---
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title: HarmonicPotential
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description: API reference for qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential
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---
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# HarmonicPotential
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<Class id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-aqua/tree/stable/0.9/qiskit/chemistry/algorithms/pes_samplers/potentials/harmonic_potential.py" signature="HarmonicPotential(molecule)" modifiers="class">
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Bases: `qiskit.chemistry.algorithms.pes_samplers.potentials.potential_base.PotentialBase`
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Implements a 1D Harmonic potential.
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Input units are Angstroms (distance between the two atoms), and output units are Hartrees (molecular energy).
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**Parameters**
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**molecule** (`Molecule`) – the underlying molecule.
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**Raises**
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**ValueError** – Only implemented for diatomic molecules
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## Methods
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### dissociation\_energy
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.dissociation_energy" signature="HarmonicPotential.dissociation_energy(scaling=1.0)">
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Returns the estimated dissociation energy for the current fit.
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**Parameters**
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**scaling** (`float`) – Scaling to change units. (Default is 1.0 for Hartrees)
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**Return type**
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`float`
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**Returns**
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estimated dissociation energy
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</Function>
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### eval
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.eval" signature="HarmonicPotential.eval(x)">
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After fitting the data to the fit function, predict the energy at a point x.
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**Parameters**
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**x** (`float`) – value to evaluate surface in
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**Return type**
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`float`
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**Returns**
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value of potential in point x
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</Function>
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### fit
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.fit" signature="HarmonicPotential.fit(xdata, ydata, initial_vals=None, bounds_list=None)">
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Fits a potential to computed molecular energies.
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**Parameters**
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* **xdata** (`List`\[`float`]) – interatomic distance points (Angstroms)
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* **ydata** (`List`\[`float`]) – molecular energies (Hartrees)
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* **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)
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* **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)
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**Return type**
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`None`
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</Function>
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### fit\_function
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.fit_function" signature="HarmonicPotential.fit_function(x, k, r_0, m_shift)" modifiers="static">
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Functional form of the potential.
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**Parameters**
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* **x** (`float`) – x parameter of harmonic potential functional form
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* **k** (`float`) – k parameter of harmonic potential functional form
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* **r\_0** (`float`) – r\_0 parameter of harmonic potential functional form
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* **m\_shift** (`float`) – m parameter of harmonic potential functional form
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**Return type**
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`float`
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**Returns**
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harmonic potential functional form
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</Function>
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### fundamental\_frequency
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.fundamental_frequency" signature="HarmonicPotential.fundamental_frequency()">
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Returns the fundamental frequency for the current fit (in s^-1).
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**Return type**
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`float`
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**Returns**
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fundamental frequency for the current fit
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</Function>
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### get\_equilibrium\_geometry
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.get_equilibrium_geometry" signature="HarmonicPotential.get_equilibrium_geometry(scaling=1.0)">
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Returns the interatomic distance corresponding to minimal energy.
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**Parameters**
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**scaling** (`float`) – Scaling to change units. (Default is 1.0 for Angstroms)
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**Return type**
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`float`
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**Returns**
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geometry corresponding to minimal energy
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</Function>
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### get\_maximum\_trusted\_level
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.get_maximum_trusted_level" signature="HarmonicPotential.get_maximum_trusted_level(n=0)">
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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).
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**Parameters**
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**n** (`int`) – vibronic mode
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**Return type**
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`float`
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**Returns**
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maximum\_trusted\_level setted
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</Function>
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### get\_minimal\_energy
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.get_minimal_energy" signature="HarmonicPotential.get_minimal_energy(scaling=1.0)">
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Returns the smallest molecular energy for the current fit.
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**Parameters**
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**scaling** (`float`) – Scaling to change units. (Default is 1.0 for Hartrees)
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**Return type**
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`float`
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**Returns**
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smallest molecular energy for the current fit
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</Function>
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### get\_num\_modes
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.get_num_modes" signature="HarmonicPotential.get_num_modes()">
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This (1D) potential represents a single vibrational mode
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**Return type**
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`int`
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</Function>
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### get\_trust\_region
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.get_trust_region" signature="HarmonicPotential.get_trust_region()">
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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.
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**Return type**
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`Tuple`\[`float`, `float`]
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</Function>
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### process\_fit\_data
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.process_fit_data" signature="HarmonicPotential.process_fit_data(xdata, ydata)" modifiers="classmethod">
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#### Mostly for internal use. Preprocesses the data passed to fit\_to\_data()
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so that only the points around the minimum are fit (which gives more accurate vibrational modes).
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**Parameters**
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* **xdata** (`List`\[`float`]) – xdata to be considered
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* **ydata** (`List`\[`float`]) – ydata to be considered
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**Return type**
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`Tuple`\[`list`, `list`]
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**Returns**
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the processed data that fit better to a harmonic potential
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</Function>
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### update\_molecule
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.update_molecule" signature="HarmonicPotential.update_molecule(molecule)">
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Updates the underlying molecule.
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**Parameters**
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**molecule** (`Molecule`) – chemistry molecule
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**Raises**
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**ValueError** – Only implemented for diatomic molecules
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**Return type**
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`Molecule`
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</Function>
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### vibrational\_energy\_level
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.vibrational_energy_level" signature="HarmonicPotential.vibrational_energy_level(n)">
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Returns the n-th vibrational energy level for the current fit (in Hartrees).
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**Parameters**
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**n** (`int`) – vibrational mode
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**Return type**
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`float`
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**Returns**
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vibrational energy level for the current fit
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</Function>
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### wave\_number
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<Function id="qiskit.chemistry.algorithms.pes_samplers.HarmonicPotential.wave_number" signature="HarmonicPotential.wave_number()">
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Returns the wave number for the current fit (in cm^-1).
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**Return type**
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`int`
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**Returns**
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wave number for the current fit
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</Function>
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</Class>
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