Dear All
I have a problem of spin polarized calculation using CASTEP all band/EDFT method.
My system is a 4-layer 2x2 Rh(111) surface. The Spin polarized calculation is supposed to give an optimized structure without spin on Rh atom. However, the spin polarized calculation shows spin at individual Rh atom, even though the total spin is zero.
Then I tried spin unpolarized calculation. It gave a different total energy, which is 2 eV higher than that of the spin polarized calculation. But as Rh does not have magnetism, the spin polarized and unpolarized calculations are supposed to give same results.
BTW, I just updated the MS a few days ago.
Here is my input for the Spin Polarized calculation of Rh(111)
task : GeometryOptimization
xc_functional : PW91
spin_polarized : true
spin : 0
opt_strategy : Default
page_wvfns : 0
cut_off_energy : 400.000000000000000
grid_scale : 1.750000000000000
fine_grid_scale : 1.750000000000000
finite_basis_corr : 0
elec_energy_tol : 1.000000000000000e-006
max_scf_cycles : 1000
fix_occupancy : false
metals_method : EDFT
num_occ_cycles : 6
nextra_bands : 18
smearing_width : 0.100000000000000
spin_fix : 6
geom_energy_tol : 2.000000000000000e-005
geom_force_tol : 0.050000000000000
geom_stress_tol : 0.100000000000000
geom_disp_tol : 0.002000000000000
geom_max_iter : 1000
geom_method : BFGS
fixed_npw : false
calculate_ELF : false
calculate_stress : false
popn_calculate : true
calculate_hirshfeld : true
calculate_densdiff : false
popn_bond_cutoff : 3.000000000000000
pdos_calculate_weights : true
num_dump_cycles : 0
The output gives the spin on individual Rh:
Rh 1 -0.80
Rh 2 0.80
Rh 3 0.68
Rh 4 -0.68
Rh 5 -0.80
Rh 6 0.80
Rh 7 0.68
Rh 8 -0.68
Rh 9 -0.80
Rh 10 0.80
Rh 11 0.68
Rh 12 -0.68
Rh 13 -0.80
Rh 14 0.80
Rh 15 0.68
Rh 16 -0.68
Well, the spin is supposed to be nearly 0, like 0.02 something.
Does any one knows the reason?
Thanks a lot
