# pair_style momb command

## Syntax

``` LAMMPS
pair_style momb cutoff s6 d
```

-   cutoff = global cutoff (distance units)
-   s6 = global scaling factor of the exchange-correlation functional
    used (unitless)
-   d = damping scaling factor of Grimme\'s method (unitless)

## Examples

``` LAMMPS
pair_style momb 12.0 0.75 20.0
pair_style hybrid/overlay eam/fs lj/charmm/coul/long 10.0 12.0 momb 12.0 0.75 20.0 morse 5.5

pair_coeff 1 2 momb 0.0 1.0 1.0 10.2847 2.361
```

## Description

Style *momb* computes pairwise van der Waals (vdW) and short-range
interactions using the Morse potential and [(Grimme)](Grimme) method
implemented in the Many-Body Metal-Organic (MOMB) force field described
comprehensively in [(Fichthorn)](Fichthorn) and [(Zhou)](Zhou5).
Grimme\'s method is widely used to correct for dispersion in density
functional theory calculations.

$$\begin{aligned}
E & = D_0 [\exp^{-2 \alpha (r-r_0)} - 2\exp^{-\alpha (r-r_0)}] - s_6 \frac{C_6}{r^6} f_{damp}(r,R_r) \\
f_{damp}(r,R_r) & = \frac{1}{1 + \exp^{-d(r/R_r - 1)}}
\end{aligned}$$

For the *momb* pair style, the following coefficients must be defined
for each pair of atoms types via the [pair_coeff](pair_coeff) command as
in the examples above, or in the data file or restart files read by the
[read_data](read_data) as described below:

-   $D_0$ (energy units)
-   $\alpha$ (1/distance units)
-   $r_0$ (distance units)
-   $C_6$ (energy\*distance\^6 units)
-   $R_r$ (distance units, typically sum of atomic vdW radii)

------------------------------------------------------------------------

## Restrictions

This style is part of the EXTRA-PAIR package. It is only enabled if
LAMMPS is built with that package. See the [Build
package](Build_package) page on for more info.

## Related commands

[pair_coeff](pair_coeff), [pair_style morse](pair_morse)

## Default

none

------------------------------------------------------------------------

::: {#Grimme}
**(Grimme)** Grimme, J Comput Chem, 27(15), 1787-1799 (2006).
:::

::: {#Fichthorn}
**(Fichthorn)** Fichthorn, Balankura, Qi, CrystEngComm, 18(29),
5410-5417 (2016).
:::

::: {#Zhou5}
**(Zhou)** Zhou, Saidi, Fichthorn, J Phys Chem C, 118(6), 3366-3374
(2014).
:::