[Pw_forum] About Iron slab calculation inputs

[Donghee Lim]

Dear QE developers and users,

I would like to ask you about some input options for iron slab calculation.
I could decide some input options based on other's advice and some 
example files as follows.
However, I am not sure whether the options are enough or other options 
are needed more for iron slab calculation. I want to refine the input 
options but I can't decide which is better than the others.

I performed some calculations with some different values of the inputs. 
Then I got some different total energy and magnetization values 
depending on different input values.
Can I say the input option that shows the lowest energy or 
magnetization values would be the most proper one?

I am especially wondering about the following input values:
- degauss = 0.01
- starting_magnetization = 0.5
- mixing_mode = 'local-TF'
- mixing_beta = 0.3
- diagonalization = 'david_overlap'
- bfgs_ndim = 3
- pot_extrapolation = 'second_order'
- wfc_extrapolation = 'second_order'
- K_point: 4 4 1  0 0 0  or  4 4 1  1 1 1 ?

Could you anyone tell me what are the criteria to determine the values, 
please?

My input file is as follows;

&CONTROL
                       title = 'Fe(100) + C2H4' ,
                 calculation = 'relax' ,
                restart_mode = 'restart' ,
                      prefix = 'ethy_fe1L' ,
                 pseudo_dir  = '/home/software/rhel4/espresso-3.1/pseudo',
                 outdir      = '/home/limkr/tmp',
                 wfcdir      = '/home/limkr/tmp2',
                     tprnfor = .true. ,
/
&SYSTEM
                       ibrav = 6,
                   celldm(1) = 10.4682D0,
                   celldm(3) = 3.16625D0,
                         nat = 16,
                        ntyp = 3,
                     ecutwfc = 35.D0 ,
                     ecutrho = 350.D0 ,
                 occupations = 'smearing' ,
                     degauss = 0.01D0 ,
                    smearing = 'methfessel-paxton' ,
                       nspin = 2 ,     starting_magnetization(3) = 0.5D0,
/
&ELECTRONS
                    conv_thr = 1.D-6 ,
                 mixing_mode = 'local-TF',
                 mixing_beta = 0.3D0 ,
             diagonalization = 'david_overlap',
            diago_david_ndim = 8,
/
&IONS
                   bfgs_ndim = 3 ,
           pot_extrapolation = 'second_order' ,
           wfc_extrapolation = 'second_order' ,
/
ATOMIC_SPECIES
    H	1.0079    H.pbe-van_ak.UPF
    C   12.011    C.pbe-van_ak.UPF
   Fe   55.84500  Fe.pbe-sp-van_ak.UPF ATOMIC_POSITIONS angstrom
C	2.1167	2.8576	2.0000	1	1	1
C	3.5984	2.8576	2.0000	1	1	1
H	1.5875	2.1167	2.0000	1	1	1
H	1.5875	3.5984	2.0000	1	1	1
H	4.1276	2.1167	2.0000	1	1	1
H	4.1276	3.5984	2.0000	1	1	1
Fe	0.0000	0.0000	0.0000	0	0	0
Fe	0.0000	2.7698	0.0000	0	0	0
Fe	2.7698	0.0000	0.0000	0	0	0
Fe	2.7698	2.7698	0.0000	0	0	0
C	-2.1167	-2.8576	-2.0000	1	1	1
C	-3.5984	-2.8576	-2.0000	1	1	1
H	-1.5875	-2.1167	-2.0000	1	1	1
H	-1.5875	-3.5984	-2.0000	1	1	1
H	-4.1276	-2.1167	-2.0000	1	1	1
H	-4.1276	-3.5984	-2.0000	1	1	1
K_POINTS automatic  4 4 1   0 0 0

Thank you,
Donghee