# Expand selection

Expands the current particle selection by selecting particles that are neighbors of already selected particles. You can choose between three different modes:

1. A cutoff radius can be specified to select particles that are within a specific maximum range of already selected particles.

2. The modifier can select particles that are among the N nearest neighbors of an already selected particle. The number N is adjustable.

3. If the system contains particle bonds, the modifier can expand the selection to particles that are bonded to at least one particle that is already selected.

## Parameters

Cutoff distance

  A particle will be selected if it is within this range of an already selected particle.

N

  The number of nearest neighbors to select around each already selected particle. OVITO sorts the list of neighbors of a selected particle by ascending distance and selects the leading N entries from the list.

Number of iterations

  This parameter allows you to expand the selection in multiple recursive steps. For example, setting this parameter to a value of 2 will expand the current selection to the second shell of neighbors, as if the modifier had been applied twice.