# Create bonds

Input: | Output:

This modifier creates bonds between particles using a cutoff radius scheme.

The appearance of bonds is controlled by an attached bonds display object. Its parameters are shown in the lower panel while the modifier is selected in the pipeline editor, or when selecting the display object itself.

## Parameters

The modifier supports two different modes that determine which pairs of particles should be connected by a bond:

Uniform cutoff radius

  Use this mode to connect particles of any type with a bond if they are closer to each other than the specified cutoff distance.

Pair-wise cutoff radii

  This mode gives you more control over which particles are connected by bonds. The table lists all pair-wise combinations of particle types. Enter a cutoff distance into the third column to connect pairs of particles of the given types with bonds. If you don't specify a cutoff for a combination of types, no bonds will be created between corresponding particles.

  Note that is mode is only available if particles carry type information.

## Technical background information

OVITO stores each bond generated by this modifier as a pair of particle indices. It makes sure that, if a particle is subsequently deleted, its bonds are deleted too. The stored particle indices of the remaining bonds are updated to reflect the changed particle sequence.

In addition to the two particle indices, OVITO stores a periodic image vector with each bond. It indicates whether a bond crosses a periodic boundary of the simulation cell. The vector of a bond that does not cross a periodic boundary is (0,0,0). A bond that crosses the cell boundary in the positive X direction, for instance, has the vector (1,0,0) and is displayed as two half bonds.