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event command

Syntax:

event Nsite site1 site2 site3 old1 old2 old3 rate new1 new2 new3 

Examples:

event	        1 tet h 1.78279E-9 he
event		1 oct h 1.78279E-9 he 
event	        2 tet tet h vac 0.98 vac h
event	        2 tet oct h vac 1.89 vac h
event	        2 tet oct vac h 0.68 h vac
event		2 tet tet he vac 0.49 vac he
event		2 oct oct he vac 1.49 vac he 
event		3 tet oct oct h vac h 0.62 h h vac
event		3 tet oct tet h vac he 1.31 he h vac
event		3 tet oct tet he h vac 0.16 h vac he
event		3 tet oct oct h vac he 0.88 he h vac
event		3 tet oct oct he h vac 0.16 h vac he 

Description:

This command defines an event for the "app_style erbium" application. It can be an event involving one, two, or three lattice sites, as specified by Nsite. The first site is the central site which owns the event. The other 2 sites (if specified) are neighors of the central site.

App_style erbium operates on a 3-fold lattice which contains fcc, tetrahedral, and octahedral sites. The site1, site2, and site3 settings specify which kinds of sites are involved in the event: fcc or tet or oct. If Nsite = 1, then only site1 is specified. If Nsite = 2, then only site1 and site2 are specified.

The old1, old2, and old3 settings specify what atoms must be on those sites in order for the event to potentially take place. The possible atoms are er for erbium, h for hydrogen, he for helium, and vac for a vacant site. E.g. in the first example above, a Hydrogen atom must be on a tetrahedral site for the event to be possible.

The rate setting determines the relative rate at which the event will occur. For Nsite=1 events, the units are inverse seconds. For Nsite=2 or Nsite=3 events, the units are energy, which is converted into a rate via the formula:

rate = exp(-energy/kT) 

where T is the temperature you have specified.

In this case the rate setting should be in the energy units defined by the application's Hamiltonian and should be consistent with the units used in the temperature command.

The new1, new2, and new3 settings specify what atoms will be on which sites if the event takes place. As with the old settings, the possible atoms are er for erbium, h for hydrogen, he for helium, and vac for a vacant site. E.g. in the first example above, a Hydrogen atom on a tetrahedral site transmutes into a Helium atom if the event takes place.

Note that the set of Nsite=1,2,3 events listed above are a reasonably full description of a reaction/diffusion model for hydrogen interstitials in an erbium lattice.

Restrictions: none

This command can only be used as part of the app_style erbium application.

Related commands:

app_style erbium

Default: none