[Pw_forum] no band gap appear in the bands eigenvalues in relaxtion though a 3 ev band gaps should be found

[Giuseppe Mattioli]

dear Xue
There are no problems! You are calculating occupied states only... Use nband=x, where x is larger than the number of occupied states.

> ecutwfc = 80.000
> 
> ecutrho = 800.0

In the case of NC pseudopotentials ecutrho is fixed by default at ecutwfc*4

HTH

Giuseppe

On Wednesday 22 May 2013 19:24:25 Yong Xue wrote:
> Dear all
> I am doing relaxation for a system of C, O, and H2 which should have a 3eV
> band gap. however, in my relaxation calculation, from the eigenvalues it
> shows no band gap. So, I cannot trust the further nmr reulst. after this
> step. I also paste my input for relax down, can anybody tell me what is the
> problem?
> as seen:
> 
> k = 0.0000 0.0000 0.0000 ( 74723 PWs) bands (ev):
> 
> -23.3453 -23.2509 -23.2259 -23.1667 -23.1380 -23.1122 -23.0976 -23.0482
> 
> -23.0458 -23.0391 -23.0106 -22.9744 -22.9539 -22.8721 -22.8682 -22.8455
> 
> -22.3021 -22.2631 -22.2033 -22.1970 -22.1484 -22.1315 -22.1282 -22.0954
> 
> -22.0871 -22.0694 -22.0552 -22.0311 -22.0123 -21.9204 -21.9035 -21.8837
> 
> -8.4344 -8.3878 -8.3473 -8.3270 -8.3022 -8.2845 -8.2588 -8.2276
> 
> -8.1713 -8.1558 -8.1257 -8.1136 -8.0572 -8.0456 -8.0142 -7.8924
> 
> -7.6997 -7.6605 -7.6189 -7.5822 -7.5252 -7.4844 -7.4585 -7.4155
> 
> -7.3812 -7.3456 -7.3208 -7.2927 -7.2727 -7.2064 -7.1959 -7.1331
> 
> -7.0934 -7.0671 -7.0557 -7.0208 -7.0045 -6.9641 -6.9386 -6.8821
> 
> -6.8590 -6.8208 -6.7835 -6.7601 -6.7139 -6.6954 -6.6775 -6.6429
> 
> -6.6383 -6.6099 -6.5706 -6.5443 -6.5219 -6.4977 -6.4694 -6.4132
> 
> -6.3866 -6.3671 -6.3464 -6.3133 -6.2895 -6.2532 -6.2271 -6.1256
> 
> -5.3074 -5.0504 -4.9293 -4.8727 -4.7052 -4.6028 -4.5628 -4.4287
> 
> -4.3984 -4.2942 -4.2714 -4.1638 -4.0900 -4.0423 -3.9205 -3.8424
> 
> -3.5850 -3.5379 -3.5217 -3.4738 -3.4482 -3.4294 -3.4036 -3.3727
> 
> -3.3479 -3.3346 -3.3131 -3.2836 -3.2617 -3.2478 -3.2094 -3.2018
> 
> -3.1871 -3.1527 -3.1299 -3.1174 -3.0990 -3.0931 -3.0428 -3.0157
> 
> -2.9912 -2.9617 -2.9398 -2.9352 -2.8936 -2.8767 -2.8479 -2.8174
> 
> 
> &CONTROL
> 
> calculation = 'relax'
> 
> restart_mode = 'from_scratch'
> 
> prefix = 'CO2-H2-recover_product_nmr'
> 
> tstress = .true.
> 
> tprnfor = .true.
> 
> nstep=500,
> 
> dt=50,
> 
> pseudo_dir = './'
> 
> outdir = './scratch/'
> 
> /
> 
> &SYSTEM
> 
> ibrav = 0
> 
> celldm(1) = 1.889726164
> 
> nat = 80
> 
> ntyp = 3
> 
> ecutwfc = 80.000
> 
> ecutrho = 800.0
> 
> nosym = .true.
> 
> /
> 
> &electrons
> 
> mixing_beta = 0.7
> 
> conv_thr = 1.0d-8
> 
> /
> 
> &IONS
> 
> ion_dynamics='bfgs'
> 
> upscale=20,
> 
> /
> 
> CELL_PARAMETERS alat
> 
> 9.9705270608830947 -0.0263506434352082 -0.3371859913906344
> 
> -0.0182095492082954 8.1336917725945508 -0.3120449570661378
> 
> -0.4215858584102301 -0.4581954945537299 11.3361129017285922
> 
> ATOMIC_SPECIES
> 
> H 1.00000 H.pbe-tm-gipaw.UPF
> 
> C 12.00000 C.pbe-tm-gipaw.UPF
> 
> O 16.00000 O.pbe-tm-gipaw.UPF
> 
> ATOMIC_POSITIONS crystal
> 
> thanks in advance
> 
> Xue


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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
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