We want to run NEB for surface calculation in gulp, but we are not able to define fsvectors and fscell. Is there any key for that? Also, if you have any examples of diffusion at grain boundaries or surfaces, kindly share them.

For the final vectors/cell, GULP already knows the dimensionality of the system from vectors, svectors, etc. Therefore the option “fvectors” handles 1-D, 2-D and 3-D. Here is the section from the help text on this option:

@@fvectors

Topic : fvectors

Type : Option

Format : fvectors

: x y z for vector 1 for 3D

: x y z for vector 2 for 3D

: x y z for vector 3 for 3D

:

: or

:

: x y z for vector 1 for 2D

: x y z for vector 2 for 2D

:

: or

:

: x y z for vector 1 for 1D

Units : Angstroms

Default : None

Use : Specifies the final unit cell for the nudged elastic band method using the cell vectors. The number of vectors must match the dimensionality of the system.

Hope that helps,

Julian