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[ramzi alaya]

Dear all,

I studied the total energy variation versus volume of the GaN and GaBi cristals, in both Zinc-blenbe au wurtzite structure. my calculation demonstrates that for the GaBi material the Zinc-blende structure is the must stable, while the wurtzite is the fundamental structure for the GaN material which is in great agreement whith the experimental results. Aiming the determination of the phase concentration variation, I also investigated the total energy variation of the GaNBi alloys for different concentration of the Bi element for both noted structures. During on calculation we were waiting for a phase transition from wurtzite to Zinc-blende structures follwing the Bi concentration increase, which is not confirmed by our main calculation fact:
We found that in fast step phase transition was from wurtzite to zinc-blende, then retured to wurtzite then to Zinc-blende increasing the concentration of Bi. 
My input is below:
 Zinc-blende structutre:

&control
    calculation='relax'
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='810-28',
    pseudo_dir = '/home/projet/pseudo/',
    outdir='/home/projet/tp/'
 /
 &system
    ibrav=  1, celldm(1) =9.00, nat= 8, ntyp= 3,
    ecutwfc =50.0, ecutrho = 200.0,
 /
 &electrons
    diagonalization='david'
    conv_thr = 1.0e-6
    mixing_beta = 0.6
 /
 &ions
 ion_dynamics='bfgs'
 /
ATOMIC_SPECIES
 Ga 69.726  Ga.pz-bhs.UPF
 n  14.0067 n_pz.upf
 bi 208.980 bi_pz.upf
ATOMIC_POSITIONS (crystal)
Ga   0.00000000   0.00000000   0.00000000
Ga   0.50000000   0.50000000   0.00000000
Ga   0.50000000   0.00000000   0.50000000
Ga   0.00000000   0.50000000   0.50000000
bi   0.25000000   0.25000000   0.25000000
bi   0.75000000   0.75000000   0.25000000
n    0.75000000   0.25000000   0.75000000
n    0.25000000   0.75000000   0.75000000
K_POINTS (automatic)
 5 5 5 1 1 1

 Wurtzite structutre:

&control
    calculation='relax'
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='5750-28',
    pseudo_dir = '/home/projet/pseudo/',
    outdir='/home/projet/tp/'
 /
 &system
    ibrav=  4, celldm(1) =6.10, celldm(3) =3.28, nat= 8, ntyp= 3,
    ecutwfc =50.0, ecutrho = 200.0,
 /
 &electrons
    diagonalization='david'
    conv_thr = 1.0e-6
    mixing_beta = 0.4
/
 &ions
 ion_dynamics='bfgs'
 /
ATOMIC_SPECIES

 Ga 69.726  Ga.pz-bhs.UPF

 n  14.0067 n_pz.upf

 bi 208.980 bi_pz.upf
ATOMIC_POSITIONS (crystal)
Ga     0.00000000   0.00000000   0.00000000
Ga     0.33333333   0.66666667   0.23787476
Ga     0.00000000   0.00000000   0.47574952
Ga     0.33333333   0.66666667   0.71362428
bi     0.00000000   0.00000000   0.17840607
bi     0.33333333   0.66666667   0.41628083
n      0.00000000   0.00000000   0.65415559
n      0.33333333   0.66666667   0.89203034
K_POINTS (automatic)
 6 6 2 1 1 1

Could you please give me some suggestions?
Thank you in advance.

ALAYA Ramzi


  		 	   		  
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