Syntax:
deposition mode rate dirx diry dirz d0 lo hi
Examples:
deposition event 1.0 0 -1 0 1.0 1 4 deposition batch 1.0 1 1 -1 1.0 3 10 deposition off
Description:
This command invokes deposition events in an on-lattice diffusion model, specified by the app_style diffusion command.
If *mode* is set to *off*, then no additional arguments are used. Deposition is turned off. This can be useful when deposition previously took place, but is now turned off.
If *mode* is set to *event*, then deposition events will be performed in tandem with diffusive hop events in the KMC diffusion model. This option only works when running on a single processor.
If *mode* is set to *batch*, then deposition events will be performed as a batch at the end of each KMC loop over sectors. Thus diffusive events and deposition events are separated. This option only works when running in parallel on multiple processors.
For each trial deposition, a random starting point at the top of the simulation box is selected (top y surface in 2d, top z surface in 3d). The atom trajectory (straight line) is traced along its incident direction which is specified by (dirx,diry,dirz) and need not be a unit vector. However, diry < 0 and dirz = 0 is required for 2d models. Similarly, dirz < 0 is required for 3d models.
Candidate deposition sites are vacant sites within a perpendicular distance d0 from the incident trajectory which also have a current coordination number C such that lo <= C <= hi. Note that d0 is specified in distance units which will depend on how the lattice of sites is defined via the lattice command. For example, if the lattice constant or box size in specified in Angstroms, then the distance units for this command are Angstroms as well.
If the inicident angle is not vertical, then periodic images of the starting point with associated incident trajectories are considered and the d0 capture distance is applied to whichever trajectory the candidate site is closest to, in a perpendicular sense. This means x-periodicity in 2d and x- and y-periodicity in 3d.
For the set of candidate sites, the selected deposition site is the one closest to the starting point, measuring the distance from the projected perpendicular point to the starting point.
IMPORTANT NOTE: App_style diffusion defines valid sites as vacant (site value = 1) or occupied (value = 2). When performing deposition, a row (2d) or plane (3d) of sites at the top of the system (where the deposited atoms are incident from) should be set to a value of 3. This prevents those sites from being considered as candidate deposition sites, due to them being neighbors of occupied sites at the bottom of the system in a periodic sense.
Restrictions:
This command can only be used as part of the app_style diffusion application.
Related commands:
Default:
The default is mode = off.