Geometry Optimisation with CASTEP

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necessarily equal to zero at the end of each BFGS step. By default a step of lambda = 1 is taken first -------------------------------------------------------------------------------- BFGS: starting iteration 1 <strong>with</strong> trial guess (lambda= 1.000000) -------------------------------------------------------------------------------- The electronic minimisation is performed and the total energy calculated. Now the line minimisation is performed +------------+-------------+-------------+-----------------+
BFGS: Final Configuration: ================================================================================ ------------------------------- Cell Contents ------------------------------- xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx x Element Atom Fractional coordinates of atoms x x Number u v w x x----------------------------------------------------------x x Si 1 0.249792 0.249792 0.250624 x x Si 2 0.000208 0.000208 -0.000624 x xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx BFGS: Final Enthalpy = -2.14845023E+002 eV The bonding information is revealing Atomic Populations ------------------ Species Ion s p d f Total Charge (e) ============================================================== Si 1 1.22 2.78 0.00 0.00 4.00 0.00 Si 2 1.22 2.78 0.00 0.00 4.00 0.00 ============================================================== Bond Population Length (A) ==================================== Si 1--Si 2 3.22 2.13974 ==================================== We can see that the bonds are sp hybridised as we might expect in Si. The bond length is 2.13974 Å. The accepted value for the Si-Si bulk bond length is 2.332 Å. Our calculation is 8% out. More about this in a later section. Next: The .geom file Up: Outputs Previous: Outputs 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
Page 9 and 10: After the atomic symbol or the atom
Page 11 and 12: KPOINTS_MP_SPACING [units] Where is
Page 13 and 14: 2005-04-04
Page 15 and 16: Next: Atomic masses Up: The .cell f
Page 17 and 18: It is possible to fix the positions
Page 19 and 20: Next: External pressure that is Up:
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: 4 -2.14844155E+002 -9.84322032E-003
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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