# Boundaries block#

This block contains information about the boundary conditions for this run. See EPOC++ input deck for more information on the input deck.

## Basics#

The `boundaries`

block sets the boundary conditions of each
boundary of the domain. Some types of boundaries allow EM wave sources
(lasers) to be attached to a boundary. Lasers are attached at the
initial conditions stage.

An example boundary block for EPOC++ is as follows:

```
begin:boundaries
bc_x_min = periodic
bc_x_max_field = periodic
bc_x_max_particle = periodic
bc_y_min = periodic
bc_y_max = periodic
end:boundaries
```

The `boundaries`

block accepts the following parameters:

`bc_{x,y,z}_min`

- The condition for the lower boundary for both fields and particles.`bc_{x,y,z}_min_{field,particle}`

- The condition for the lower boundary for {fields,particles}.`bc_{x,y,z}_max`

- The condition for the upper boundary for both fields and particles.`bc_{x,y,z}_max_{field,particle}`

- The condition for the upper boundary for {fields,particles}.

There are several boundary types in EPOC++ and each boundary of the domain can have one and only one of these boundaries attached to it. These boundary types are:

`periodic`

- A simple periodic boundary condition. Fields and/or particles reaching one edge of the domain are wrapped round to the opposite boundary. If either boundary condition is set to periodic then the boundary condition on the matching boundary at the other side of the box is also assumed periodic.`laser`

- A boundary to which one or more EM wave sources can be attached. EM waves impinging on a*laser*boundary are transmitted with as little reflection as possible using the`open`

absorbing boundary condition. Particles are transmitted through the boundary and removed from the system. simulation when they reach the boundary. See Laser blocks for details.`open`

- When applied to fields, EM waves outflowing characteristics propagate through the boundary. Particles are transmitted through the boundary and removed from the system.