Cutoff Functions¶
The cutoffs module gives a few different options for smoothly sending the GP kernel to zero near the boundary of the cutoff sphere.
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flare.kernels.cutoffs.
cosine_cutoff
(r_cut: float, ri: float, ci: float, d: float = 1)¶ A cosine cutoff that returns 1 up to r_cut - d, and assigns a cosine envelope to values of r between r_cut - d and r_cut. Based on Eq. 24 of Albert P. Bartók and Gábor Csányi. “Gaussian approximation potentials: A brief tutorial introduction.” International Journal of Quantum Chemistry 115.16 (2015): 1051-1057.
Parameters: - r_cut (float) – Cutoff value (in angstrom).
- ri (float) – Interatomic distance.
- ci (float) – Cartesian coordinate divided by the distance.
Returns: Cutoff value and its derivative.
Return type: (float, float)
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flare.kernels.cutoffs.
cubic_cutoff
(r_cut: float, ri: float, ci: float)¶ A cubic cutoff that goes to zero smoothly at the cutoff boundary.
Parameters: - r_cut (float) – Cutoff value (in angstrom).
- ri (float) – Interatomic distance.
- ci (float) – Cartesian coordinate divided by the distance.
Returns: Cutoff value and its derivative.
Return type: (float, float)
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flare.kernels.cutoffs.
hard_cutoff
(r_cut: float, ri: float, ci: float)¶ A hard cutoff that assigns a value of 1 to all interatomic distances.
Parameters: - r_cut (float) – Cutoff value (in angstrom).
- ri (float) – Interatomic distance.
- ci (float) – Cartesian coordinate divided by the distance.
Returns: Cutoff value and its derivative.
Return type: (float, float)
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flare.kernels.cutoffs.
quadratic_cutoff
(r_cut: float, ri: float, ci: float)¶ A quadratic cutoff that goes to zero smoothly at the cutoff boundary.
Parameters: - r_cut (float) – Cutoff value (in angstrom).
- ri (float) – Interatomic distance.
- ci (float) – Cartesian coordinate divided by the distance.
Returns: Cutoff value and its derivative.
Return type: (float, float)
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flare.kernels.cutoffs.
quadratic_cutoff_bound
(r_cut: float, ri: float, ci: float)¶ A quadratic cutoff that goes to zero smoothly at the cutoff boundary.
Parameters: - r_cut (float) – Cutoff value (in angstrom).
- ri (float) – Interatomic distance.
- ci (float) – Cartesian coordinate divided by the distance.
Returns: Cutoff value and its derivative.
Return type: (float, float)