# BUCK4RANGES

Section can be repeated.

This section specifies the input parameters for the Buckingham 4-ranges potential type.

Range | Functional Form
--- | ---
\( r < r_1 \) | \( V(r) = A\exp(-Br) \)
\( r_1 \leq r < r_2 \) | \( V(r) = \sum_n \operatorname{POLY1}(n)r_n \)
\( r_2 \leq r < r_3 \) | \( V(r) = \sum_n \operatorname{POLY2}(n)r_n \)
\( r \geq r_3 \) | \( V(r) = -C/r_6 \)

[Edit on GitHub]

## Keywords

- A

- ATOMS

- B

- C

- POLY1

- POLY2

- R1

- R2

- R3

- RCUT

- RMAX

- RMIN

## Keyword descriptions

A: real = [K_e]

  Usage: A {real}

  Defines the A parameter of the Buckingham potential [Edit on GitHub]

ATOMS: string[2]

  Usage: ATOMS {KIND1} {KIND2}

  Defines the atomic kind involved in the nonbond potential [Edit on GitHub]

B: real = [angstrom^-1]

  Usage: B {real}

  Defines the B parameter of the Buckingham potential [Edit on GitHub]

C: real = [angstrom^6*K_e]

  Usage: C {real}

  Defines the C parameter of the Buckingham potential [Edit on GitHub]

POLY1: real[ ] = [K_e]

  Keyword can be repeated.

  Usage: POLY1 C1 C2 C3 ..

  Coefficients of the polynomial used in the second range This keyword can be repeated several times. [Edit on GitHub]

POLY2: real[ ] = [K_e]

  Keyword can be repeated.

  Usage: POLY2 C1 C2 C3 ..

  Coefficients of the polynomial used in the third range This keyword can be repeated several times. [Edit on GitHub]

R1: real = [angstrom]

  Usage: R1 {real}

  Defines the upper bound of the first range [Edit on GitHub]

R2: real = [angstrom]

  Usage: R2 {real}

  Defines the upper bound of the second range [Edit on GitHub]

R3: real = [angstrom]

  Usage: R3 {real}

  Defines the upper bound of the third range [Edit on GitHub]

RCUT: real = 1.00000000E+001 [angstrom]

  Usage: RCUT {real}

  Defines the cutoff parameter of the Buckingham potential [Edit on GitHub]

RMAX: real = [angstrom]

  Usage: RMAX {real}

  Defines the upper bound of the potential. If not set the range is the full range generate by the spline [Edit on GitHub]

RMIN: real = [angstrom]

  Usage: RMIN {real}

  Defines the lower bound of the potential. If not set the range is the full range generate by the spline [Edit on GitHub]