howto:running_qe_computation
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howto:running_qe_computation [2019/08/18 13:50] – [Cell relaxation] mtaillefumier | howto:running_qe_computation [2019/09/02 08:10] – [Molecular dynamics] mtaillefumier | ||
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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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^ QE input ^ CP2K input ^ | ^ QE input ^ CP2K input ^ | ||
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- | 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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</ | </ | ||
- | ===== Cell relaxation | + | ===== Molecular dynamics |
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- | 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 | + | |
+ | 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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</ | </ | ||
- | you should obtain a file '' | + | you should obtain a file '' |
- | {{ :howto:si7ge-md.pdf |}} | + | {{:howto:cp2k-sirius-md.png|}} |
+ | 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