[Pw_forum] vc_relax

Samin, Adib J. samin.2 at buckeyemail.osu.edu
Mon Dec 15 17:50:20 CET 2014


Dear Quantum Espresso Users,


I am studying the material (Li4Ti5O12) (an anode material for the Lithium ion battery). First of all, the band gap I am calculating is (2.8 eV) as opposed to the reported range from DFT calculations (1.7-2.3 eV). Moreover, I am interested in calculating the intercalation potential using the formula:


V = (E(Li7Ti5O12)-E(Li4Ti5O12)-3Ebcc(Li))/(x F)     ;   where F is the Faraday constant and x is the number of added moles


I think I am using better parameters than what has been reported in the literature. Still, the intercalation potential I am calculating is (1.19)V compared with the reported range in the literature (1.4-1.6) V.


I am not sure what else I can change to make the calculation better. I thought of using a Hubbard U but none of the papers report using that. Furthermore, I am using the same cell size and same k-point sampling as used in the literature.


Any suggestions or recommendations would be much appreciated


&control
    calculation='vc-relax'
    restart_mode='from_scratch',
    prefix='Li4_333',
    pseudo_dir = '/usr/local/espresso/espresso-5.0.3/pseudo/',
    outdir='/fs/lustre/osu7838/LiTiO/ecut1'
    tstress=.true.
    tprnfor=.true.
    wf_collect=.true.
/
&system
    ibrav=0, nat=168, ntyp=3, nbnd=716,
    ecutwfc=60, ecutrho=600,
    occupations='smearing', smearing='gaussian', degauss=0.003,
/
&electrons
    mixing_beta = 0.3
/
&ions
/
&cell
/
CELL_PARAMETERS {angstrom}
8.3595 0.0 0.0
0.0 8.3595 0.0
0.0 0.0 25.0785
ATOMIC_SPECIES
Li 6.941 Li.pbe-s-van_ak.UPF
Ti 47.867 Ti.pbe-sp-van_ak.UPF
O 15.9994 O.pbe-van_ak.UPF
ATOMIC_POSITIONS {crystal}
Li  0  0  0
Li  0  0  0.333333333
Li  0  0  0.666666667
Li  0  0.5  0.166666667
Li  0  0.5  0.5
Li  0  0.5  0.833333333
Li  0.25  0.25  0.083333333
Li  0.25  0.25  0.416666667
Li  0.25  0.25  0.75
Li  0.25  0.75  0.25
Li  0.25  0.75  0.583333333
Li  0.25  0.75  0.916666667
Li  0.5  0  0.166666667
Li  0.5  0  0.5
Li  0.5  0  0.833333333
Li  0.5  0.5  0
Li  0.5  0.5  0.333333333
Li  0.5  0.5  0.666666667
Li  0.75  0.25  0.25
Li  0.75  0.25  0.583333333
Li  0.75  0.25  0.916666667
Li  0.75  0.75  0.083333333
Li  0.75  0.75  0.416666667
Li  0.75  0.75  0.75
O  0.1122  0.1122  0.129266667
O  0.1122  0.1122  0.4626
O  0.1122  0.1122  0.795933333
O  0.1122  0.3878  0.0374
O  0.1122  0.3878  0.370733333
O  0.1122  0.3878  0.704066667
O  0.1122  0.6122  0.295933333
O  0.1122  0.6122  0.629266667
O  0.1122  0.6122  0.9626
O  0.1122  0.8878  0.204066667
O  0.1122  0.8878  0.5374
O  0.1122  0.8878  0.870733333
O  0.1378  0.1378  0.2874
O  0.1378  0.1378  0.620733333
O  0.1378  0.1378  0.954066667
O  0.1378  0.3622  0.2126
O  0.1378  0.3622  0.545933333
O  0.1378  0.3622  0.879266667
O  0.1378  0.6378  0.120733333
O  0.1378  0.6378  0.454066667
O  0.1378  0.6378  0.7874
O  0.1378  0.8622  0.045933333
O  0.1378  0.8622  0.379266667
O  0.1378  0.8622  0.7126
O  0.3622  0.1378  0.2126
O  0.3622  0.1378  0.545933333
O  0.3622  0.1378  0.879266667
O  0.3622  0.3622  0.2874
O  0.3622  0.3622  0.620733333
O  0.3622  0.3622  0.954066667
O  0.3622  0.6378  0.045933333
O  0.3622  0.6378  0.379266667
O  0.3622  0.6378  0.7126
O  0.3622  0.8622  0.120733333
O  0.3622  0.8622  0.454066667
O  0.3622  0.8622  0.7874
O  0.3878  0.1122  0.0374
O  0.3878  0.1122  0.370733333
O  0.3878  0.1122  0.704066667
O  0.3878  0.3878  0.129266667
O  0.3878  0.3878  0.4626
O  0.3878  0.3878  0.795933333
O  0.3878  0.6122  0.204066667
O  0.3878  0.6122  0.5374
O  0.3878  0.6122  0.870733333
O  0.3878  0.8878  0.295933333
O  0.3878  0.8878  0.629266667
O  0.3878  0.8878  0.9626
O  0.6122  0.1122  0.295933333
O  0.6122  0.1122  0.629266667
O  0.6122  0.1122  0.9626
O  0.6122  0.3878  0.204066667
O  0.6122  0.3878  0.5374
O  0.6122  0.3878  0.870733333
O  0.6122  0.6122  0.129266667
O  0.6122  0.6122  0.4626
O  0.6122  0.6122  0.795933333
O  0.6122  0.8878  0.0374
O  0.6122  0.8878  0.370733333
O  0.6122  0.8878  0.704066667
O  0.6378  0.1378  0.120733333
O  0.6378  0.1378  0.454066667
O  0.6378  0.1378  0.7874
O  0.6378  0.3622  0.045933333
O  0.6378  0.3622  0.379266667
O  0.6378  0.3622  0.7126
O  0.6378  0.6378  0.2874
O  0.6378  0.6378  0.620733333
O  0.6378  0.6378  0.954066667
O  0.6378  0.8622  0.2126
O  0.6378  0.8622  0.545933333
O  0.6378  0.8622  0.879266667
O  0.8622  0.1378  0.045933333
O  0.8622  0.1378  0.379266667
O  0.8622  0.1378  0.7126
O  0.8622  0.3622  0.120733333
O  0.8622  0.3622  0.454066667
O  0.8622  0.3622  0.7874
O  0.8622  0.6378  0.2126
O  0.8622  0.6378  0.545933333
O  0.8622  0.6378  0.879266667
O  0.8622  0.8622  0.2874
O  0.8622  0.8622  0.620733333
O  0.8622  0.8622  0.954066667
O  0.8878  0.1122  0.204066667
O  0.8878  0.1122  0.5374
O  0.8878  0.1122  0.870733333
O  0.8878  0.3878  0.295933333
O  0.8878  0.3878  0.629266667
O  0.8878  0.3878  0.9626
O  0.8878  0.6122  0.0374
O  0.8878  0.6122  0.370733333
O  0.8878  0.6122  0.704066667
O  0.8878  0.8878  0.129266667
O  0.8878  0.8878  0.4626
O  0.8878  0.8878  0.795933333
Ti  0.125  0.125  0.208333333
Ti  0.125  0.125  0.541666667
Ti  0.125  0.125  0.875
Li  0.125  0.375  0.291666667
Ti  0.125  0.375  0.625
Ti  0.125  0.375  0.958333333
Ti  0.125  0.625  0.041666667
Ti  0.125  0.625  0.375
Ti  0.125  0.625  0.708333333
Ti  0.125  0.875  0.125
Ti  0.125  0.875  0.458333333
Li  0.125  0.875  0.791666667
Ti  0.375  0.125  0.291666667
Ti  0.375  0.125  0.625
Ti  0.375  0.125  0.958333333
Ti  0.375  0.375  0.208333333
Li  0.375  0.375  0.541666667
Ti  0.375  0.375  0.875
Ti  0.375  0.625  0.125
Ti  0.375  0.625  0.458333333
Ti  0.375  0.625  0.791666667
Li  0.375  0.875  0.041666667
Ti  0.375  0.875  0.375
Ti  0.375  0.875  0.708333333
Ti  0.625  0.125  0.041666667
Ti  0.625  0.125  0.375
Li  0.625  0.125  0.708333333
Ti  0.625  0.375  0.125
Ti  0.625  0.375  0.458333333
Ti  0.625  0.375  0.791666667
Li  0.625  0.625  0.208333333
Ti  0.625  0.625  0.541666667
Ti  0.625  0.625  0.875
Ti  0.625  0.875  0.291666667
Ti  0.625  0.875  0.625
Ti  0.625  0.875  0.958333333
Ti  0.875  0.125  0.125
Li  0.875  0.125  0.458333333
Ti  0.875  0.125  0.791666667
Ti  0.875  0.375  0.041666667
Ti  0.875  0.375  0.375
Ti  0.875  0.375  0.708333333
Ti  0.875  0.625  0.291666667
Ti  0.875  0.625  0.625
Li  0.875  0.625  0.958333333
Ti  0.875  0.875  0.208333333
Ti  0.875  0.875  0.541666667
Ti  0.875  0.875  0.875
K_POINTS {automatic}
3 3 1 0 0 0

+++++++++++++++++++++++++++++++++++++++++++++
Adib Samin
Postdoctoral Researcher
The Ohio State Univsersity
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