# atsim.potentials.potentialforms¶

Functions representing different potential forms.

The functions contained herein are function factories returning a function that takes separation as its sole argument.

See List of Potential Forms for descriptions of these potential forms.

## Module Contents¶

### Functions¶

 potential(func) Decorator for callables that should be tagged as potential-forms or potential-functions is_potential(obj) Identifies if an object is a potential-form or potential-function buck4(A, rho, C, r_detach, r_min, r_attach) Returns a potential form describing the four-range Buckingham potential.
atsim.potentials.potentialforms.potential(func)[source]

Decorator for callables that should be tagged as potential-forms or potential-functions

atsim.potentials.potentialforms.is_potential(obj)[source]

Identifies if an object is a potential-form or potential-function

atsim.potentials.potentialforms.buck4(A, rho, C, r_detach, r_min, r_attach)[source]

Returns a potential form describing the four-range Buckingham potential.

The potential form is:

$\begin{split}V(r_{ij}) = \begin{cases} A \exp(-r_{ij}/\rho) , & 0 \leq r_{ij} \leq r_\text{detach}\\ a_0 + a_1 r_{ij} +a_2 r_{ij}^2+a_3 r_{ij}^3+a_4 r_{ij}^4+a_5 r_{ij}^5, & r_\text{detach} < r_{ij} < r_\text{min}\\ b_0 +b_1 *r_{ij}+b_2*r_{ij}^2+b_3*r_{ij}^3 , & r_\text{min} \leq r_{ij} < r_\text{attach}\\ -\frac{C}{r_{ij}^6} , & r_{ij} \geq r_\text{attach}\\ \end{cases}\end{split}$

In other words this is a Buckingham potential in which the Born-Mayer component acts at small separations and the disprsion term acts at larger separation. These two parts are linked by a fifth then third order polynomial (with a minimum formed in the spline at $$r_ ext{min}$$).

The spline parameters are subject to the constraints that $$V(r_{ij})$$, first and second derivatives must be equal at the boundary points and the function must have a stationary point at r_min.

• atsim.potentials.Buck4_Spline
• atsim.potentials.Buck4_SplinePotential

Note

Due to the complexity of calculating the spline-coefficients this potential form does not have an equivalent in the atsim.potentials.potentialfunctions module.

Parameters: A – A potential parameter. rho – potential parameter. C – C parameter. r_detach – Separation where spline starts. r_min – Location of stationary point. r_attach – End of splined region. Splined potential.
atsim.potentials.potentialforms.buck[source]
atsim.potentials.potentialforms.bornmayer[source]
atsim.potentials.potentialforms.coul[source]
atsim.potentials.potentialforms.constant[source]
atsim.potentials.potentialforms.exponential[source]
atsim.potentials.potentialforms.hbnd[source]
atsim.potentials.potentialforms.lj[source]
atsim.potentials.potentialforms.morse[source]
atsim.potentials.potentialforms.polynomial[source]
atsim.potentials.potentialforms.sqrt[source]
atsim.potentials.potentialforms.tang_toennies[source]
atsim.potentials.potentialforms.zbl[source]
atsim.potentials.potentialforms.zero[source]
atsim.potentials.potentialforms.exp_spline[source]