howto:running_qe_computation
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howto:running_qe_computation [2019/08/13 12:50] – mtaillefumier | howto:running_qe_computation [2019/12/23 20:54] – oschuett | ||
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+ | ====== How to do calculations like Quantum ESPRESSO ====== | ||
+ | |||
+ | |||
===== Introduction ===== | ===== Introduction ===== | ||
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An other popular program for plane wave DFT is [[http:// | An other popular program for plane wave DFT is [[http:// | ||
SIRIUS. We will consider the simple case of silicium doped with germanium and | SIRIUS. We will consider the simple case of silicium doped with germanium and | ||
- | show how to convert a QE input file to cp2k input file. Files for this tutorial can be found [[https:// | + | show how to convert a QE input file to cp2k input file. Files for this tutorial can be found [[https:// |
=== Word of caution with the pseudo-potential files === | === Word of caution with the pseudo-potential files === | ||
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/ | / | ||
&system | &system | ||
- | ibrav=0, celldm(1)=1, | + | ibrav=0, celldm(1)=1, |
- | ecutrho = 300, occupations = ' | + | ecutrho = 400, occupations = ' |
smearing = ' | smearing = ' | ||
nat=8 ntyp=2 | nat=8 ntyp=2 | ||
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- | | + | |
- | | + | |
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for cp2k input file. Note the presence of the keyword '' | for cp2k input file. Note the presence of the keyword '' | ||
which indicates that cp2k should treat the coordinates as given in the lattice | which indicates that cp2k should treat the coordinates as given in the lattice | ||
- | basis. Putting these two sections together, we have | + | basis. **The coordinates do not have to be given in the lattice basis, any format supported by cp2k will work**. Putting these two sections together, we have |
< | < | ||
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^ QE input ^ CP2K input ^ | ^ QE input ^ CP2K input ^ | ||
|< | |< | ||
- | ecutwfc=30 | + | ecutwfc=25 |
- | ecutrho = 300 | + | ecutrho = 400 |
</ | </ | ||
& | & | ||
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& | & | ||
| | ||
- | | + | |
- | | + | |
&END PARAMETERS | &END PARAMETERS | ||
&END PW_DFT | &END PW_DFT | ||
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& | & | ||
| | ||
- | | + | |
- | | + | |
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Energy | Energy | ||
-------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- | ||
- | valence_eval_sum | + | valence_eval_sum |
- | < | + | < |
- | < | + | < |
< | < | ||
- | < | + | < |
- | one-electron contribution : -81.39606791 | + | one-electron contribution : -81.17469111 |
- | hartree contribution | + | hartree contribution |
- | xc contribution | + | xc contribution |
- | ewald contribution | + | ewald contribution |
PAW contribution | PAW contribution | ||
- | Total energy | + | Total energy |
- | band gap (eV) : 0.36618436 | + | band gap (eV) : 0.34564591 |
- | Efermi | + | Efermi |
- | iteration : | + | iteration : |
- | converged after 11 SCF iterations! | + | converged after 12 SCF iterations! |
- | + | ||
- | | + | |
+ | | ||
</ | </ | ||
- | ===== Cell relaxation | + | ===== Molecular dynamics |
- | + | ||
- | Quantum expresso supports many types of calculations that cp2k supports natively. For instance, it is possible to do cell relaxation in cp2k with the sirius backend, something that QE can do as well. The following QE input file | + | |
- | < | + | |
- | & | + | |
- | calculation=' | + | |
- | restart_mode=' | + | |
- | pseudo_dir = ' | + | |
- | outdir=' | + | |
- | prefix = ' | + | |
- | tstress = false, | + | |
- | tprnfor = false, | + | |
- | verbosity = ' | + | |
- | wf_collect = false | + | |
- | / | + | |
- | & | + | |
- | ibrav=0, celldm(1)=1, | + | |
- | occupations = ' | + | |
- | nat=8 ntyp=2 | + | |
- | / | + | |
- | & | + | |
- | conv_thr = 1.0d-11, | + | |
- | mixing_beta = 0.7, | + | |
- | electron_maxstep = 100 | + | |
- | / | + | |
- | &IONS | + | |
- | ion_dynamics=' | + | |
- | / | + | |
- | &CELL | + | |
- | cell_dynamics=' | + | |
- | / | + | |
- | ATOMIC_SPECIES | + | |
- | Ge 0.0 ge_lda_v1.uspp.F.UPF | + | |
- | Si 0.0 si_lda_v1.uspp.F.UPF | + | |
- | CELL_PARAMETERS | + | |
- | | + | |
- | 0.00000000 | + | |
- | 0.00000000 | + | |
- | ATOMIC_POSITIONS (crystal) | + | |
- | Ge 0.00000000 | + | |
- | Si 0.00000000 | + | |
- | Si 0.50000000 | + | |
- | Si 0.50000000 | + | |
- | Si 0.75000000 | + | |
- | Si 0.75000000 | + | |
- | Si 0.25000000 | + | |
- | Si 0.25000000 | + | |
- | K_POINTS (automatic) | + | |
- | 2 2 2 0 0 0 | + | |
- | </ | + | |
- | + | ||
- | describes the computation of the cell relaxation for Si7Ge for instance. The cp2k input file for the sirius backend will look like | + | |
+ | Quantum expresso supports many types of calculations that cp2k supports natively. For instance, it is possible to do molecular dynamics in cp2k with the sirius backend, something that QE can do as well. To do this, we can start from the previous cp2k input file for Si7Ge and add a small section for setting the parameters relevant for the molecular dynamics. The '' | ||
+ | |||
< | < | ||
& | & | ||
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- | | + | |
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- | | + | |
- | | + | |
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OPTIMIZER LBFGS | OPTIMIZER LBFGS | ||
& | & | ||
+ | & | ||
+ | ENSEMBLE NVE | ||
+ | TIMESTEP 0.1 | ||
+ | STEPS 125 | ||
+ | TEMPERATURE 300.0 | ||
+ | & | ||
&END MOTION | &END MOTION | ||
&GLOBAL | &GLOBAL | ||
PROJECT Si7Ge | PROJECT Si7Ge | ||
PRINT_LEVEL MEDIUM | PRINT_LEVEL MEDIUM | ||
- | RUN_TYPE | + | RUN_TYPE |
&END GLOBAL | &END GLOBAL | ||
</ | </ | ||
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</ | </ | ||
- | you should obtain a file '' | + | you should obtain a file '' |
+ | {{: | ||
+ | The total energy given by QE and CP2K/SIRIUS are shifted by a small offset. More generally, converting the input file from QE to CP2K is not a warranty to obtain the same results for the total energy. The reasons for this multiple : | ||
+ | * Indicating the same cutoff does not warranty the fft grid size. | ||
+ | * QE and SIRIUS treat the radial integrals interpolation differently | ||
+ | * The functional in QE do not use libxc by default, while CP2K/SIRIUS does. | ||
+ | * The minimization method is sensitive to the initial states. | ||
+ | For all these reasons, we should not try to compare results at the binary level. |
howto/running_qe_computation.txt · Last modified: 2021/12/08 10:18 by mtaillefumier