## neighbor

### Syntax

```
neighbor bin_size neighbor_freq
```

`bin_size`

= non-negative real number`neighbor_freq`

= positive integer

### Examples

```
neighbor 1. 100
neighbor 2. 200
```

### Description

This command sets parameters for updating the neighbor list. In CAC simulatoins, each atom in the atomistic domain and each integration point in the coarse-grained domain maintain neighbor lists. Note that the non-integration point interpolated atoms in the coarse-grained domain do not maintain neighbor lists because their force/energy etc. are not calculated.

`bin_size`

, in Angstrom, sets the length of the bin, which adds to the cutoff distance $r_\mathrm{c}$ of the interatomic potential. All atoms within $r_\mathrm{c}$ + `bin_size`

from an atom/integration point are the neighbors of this atom. Note that each edge length of the processor domain cannot be smaller than $2 \cdot$ ($r_\mathrm{c}$ + `bin_size`

).

`neighbor_freq`

is the frequency with which a check of whether the neighbor list should be updated is conducted. The neighbor lists of all atoms/integration points are updated if, with respect to the nodal/atomic positions recorded at the last check, any node or atom has a displacement larger than half the `bin_size`

.

### Related commands

The initial number of neighboring atoms per atom/integration point is set in the limit command.

### Related files

`neighbor_init.f90`

and `update_neighbor.f90`

### Default

```
neighbor 1. 200
```