Geometry Optimisation with CASTEP

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Next: Cell symmetry Up: The .cell file and Previous: The Initial Configuration of The k-point sampling grid The points in k-space at which the Brillouin zone is to be sampled can be defined in one of three ways. As a list %BLOCK KPOINTS_LIST units %BLOCK KPOINTS_LIST The first three numbers on a line are the co-ordinates of a k-point as fractions of the relevent reciprocal space lattice vector. The final number is a weight for the k-point. The weights of all n k-points must add up to 1. Another way is to use a Monkhurst-Pack grid and there are two ways of doing this. The first way is to specify the grid dimensions in the three directions of the reciprocal space lattice vectors KPOINTS_MP_GRID So, for example, we could have a 2x2x2 grid or a 3x4x1 grid. The choice depends upon computational resources and whether a more detailed sampling of the electronic wave function is required in a given reciprocal space direction. A second way of requesting a Monkhurst-Pack grid is to specify a minimum grid density.
KPOINTS_MP_SPACING [units] Where is the maximum distance between any two k-points in the grid. The default [units] of the k- point spacing are Å . Another feature of the Monkhurst-Pack grid that the user can specify is the alignment of the grid <strong>with</strong> respect to the origin of the Brillouin zone. By including KPOINT_MP_OFFSET the Monkhurst-Pack grid can be offset from the origin of the Brillouin zone. The entries are the fractions of the reciprocal space lattice vector that give the value of the offset in the three directions. Next: Cell symmetry Up: The .cell file and Previous: The Initial Configuration of 2005-04-04
Page 1 and 2: Next: Recipe Geometry Optimisation
Page 3 and 4: Next: Inputs Up: Geometry Optimisat
Page 5 and 6: Next: The Size and Shape Up: Inputs
Page 7 and 8: In both cases if [units] are not sp
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Page 15 and 16: Next: Atomic masses Up: The .cell f
Page 17 and 18: It is possible to fix the positions
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Page 21 and 22: Next: General Job Parameters Up: In
Page 23 and 24: When a calculation that was stopped
Page 25 and 26: Next: Electronic Minimisation Param
Page 27 and 28: Next: Example - Bulk Silicon Up: Th
Page 29 and 30: the default value is 3 but it must
Page 31 and 32: We must now choose a supercell to e
Page 33 and 34: Next: The .castep file Up: Geometry
Page 35 and 36: 4 -2.14844155E+002 -9.84322032E-003
Page 37 and 38: BFGS: Final Configuration: ========
Page 39 and 40: Next: Other output files Up: Output
Page 41 and 42: Next: A Variable Cell calculation U
Page 43 and 44: arbitrary set of basis set paramete
Page 45 and 46: 3 -2.16474423E+002 2.10512829E-007
Page 47 and 48: Figure 6:A finite vacuum gap may ca
Page 49 and 50: 0.0000000000 0.0000000000 24.503725
Page 51 and 52: thickness We can see that the total
Page 53 and 54: It is interesting to look at the ev
Page 55 and 56: Next: About this document ... Up: G

Geometry Optimisation with CASTEP

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