howto:gw
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howto:gw [2021/04/21 20:43] – [4. Self-consistent GW calculations] jwilhelm | howto:gw [2021/04/21 20:51] – jwilhelm | ||
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===== 4. Self-consistent GW calculations and DFT starting point ===== | ===== 4. Self-consistent GW calculations and DFT starting point ===== | ||
- | The G0W0@PBE HOMO value of the H2O molecule (~ -12.0 eV) is not in good agreement with the experimental ionization potential (12.62 eV). Benchmarks on molecules and solids indicate that self-consistency of eigenvalues in the Green' | + | The G0W0@PBE HOMO value of the H2O molecule (~ -12.0 eV) is not in good agreement with the experimental ionization potential (12.62 eV). Benchmarks on molecules and solids indicate that self-consistency of eigenvalues in the Green' |
+ | |||
+ | You can run GW0 calculations in CP2K by putting | ||
+ | < | ||
+ | &GW | ||
+ | SC_GW0_ITER | ||
+ | CORR_OCC | ||
+ | CORR_VIRT | ||
+ | RI_SIGMA_X | ||
+ | &END GW | ||
+ | </ | ||
+ | " | ||
===== 5. Periodic GW calculations ===== | ===== 5. Periodic GW calculations ===== | ||
- | For periodic GW calculations, | + | For periodic GW calculations, |
- | The basis can be found in {{exercises: | + | The basis can be found in {{exercises: |
<code - LiH_periodic.inp> | <code - LiH_periodic.inp> | ||
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&END XC_FUNCTIONAL | &END XC_FUNCTIONAL | ||
& | & | ||
- | METHOD | ||
&RI_RPA | &RI_RPA | ||
- | | + | |
- | GW | + | |
- | & | + | |
| | ||
| | ||
! activate the periodic correction | ! activate the periodic correction | ||
| | ||
- | | + | & |
- | | + | |
- | | + | |
! HF calculation for the exchange part of the self-energy | ! HF calculation for the exchange part of the self-energy | ||
! Here, the truncation of the Coulomb operator works | ! Here, the truncation of the Coulomb operator works | ||
Line 233: | Line 241: | ||
&KIND H | &KIND H | ||
BASIS_SET cc-DZVP-GTH | BASIS_SET cc-DZVP-GTH | ||
- | | + | |
POTENTIAL GTH-PBE-q1 | POTENTIAL GTH-PBE-q1 | ||
&END KIND | &END KIND | ||
&KIND Li | &KIND Li | ||
BASIS_SET cc-DZVP-GTH | BASIS_SET cc-DZVP-GTH | ||
- | | + | |
POTENTIAL GTH-PBE-q3 | POTENTIAL GTH-PBE-q3 | ||
&END KIND | &END KIND | ||
Line 247: | Line 255: | ||
PRINT_LEVEL MEDIUM | PRINT_LEVEL MEDIUM | ||
RUN_TYPE ENERGY | RUN_TYPE ENERGY | ||
- | &END GLOBAL | ||
- | </ | ||
- | |||
- | |||
- | ===== 6. Cubic-scaling GW calculations ===== | ||
- | Cubic-scaling GW calculations could be a more efficient alternative for large systems. See below an exemplary input for one water molecule. Compare the results to the ones from Sec. 1. In general, small deviations (< 0.05 eV) for GW levels can be expected from cubic-scaling GW calculations compared to canonical GW calculations due to additional approximations in cubic-scaling GW. | ||
- | |||
- | Please observe that the input below is much slower than the input for canonical GW. Therefore, it can be beneficial to run it with more MPI tasks. The beneficial scaling of cubic-scaling GW only pays off for large systems where it is more efficient as canonical GW calculations (rule of thumb: cubic-scaling GW can be more efficient for systems with more than 100 atoms if the filter parameters are well set). | ||
- | |||
- | <code - H2O_GW100_cubic_scaling.inp> | ||
- | & | ||
- | METHOD Quickstep | ||
- | &DFT | ||
- | ! retrieve basis set from the CP2K trunk version | ||
- | BASIS_SET_FILE_NAME BASIS_def2_QZVP_RI_ALL | ||
- | POTENTIAL_FILE_NAME POTENTIAL | ||
- | &MGRID | ||
- | CUTOFF 400 | ||
- | REL_CUTOFF 50 | ||
- | &END MGRID | ||
- | &QS | ||
- | ! all electron calculation since GW100 is all-electron test | ||
- | METHOD GAPW | ||
- | &END QS | ||
- | & | ||
- | PERIODIC NONE | ||
- | PSOLVER MT | ||
- | &END | ||
- | &SCF | ||
- | EPS_SCF 1.0E-6 | ||
- | SCF_GUESS ATOMIC | ||
- | MAX_SCF 200 | ||
- | &END SCF | ||
- | &XC | ||
- | & | ||
- | &END XC_FUNCTIONAL | ||
- | & | ||
- | METHOD RI_RPA_GPW | ||
- | ERI_METHOD OS | ||
- | ! cubic-scaling GW only works with overlap metric RI | ||
- | RI OVERLAP | ||
- | & | ||
- | ! EPS_FILTER should be tuned for the specific application: | ||
- | ! the computational cost strongly depends on EPS_FILTER | ||
- | EPS_FILTER 1.0E-12 | ||
- | ! EPS_GRID may be tuned since memory is weakly | ||
- | ! dependent on it | ||
- | EPS_GRID | ||
- | &END WFC_GPW | ||
- | &RI_RPA | ||
- | ! cubic-scaling GW only works with the minimax grid | ||
- | ! in imag. time and frequency | ||
- | MINIMAX | ||
- | ! If the HOMO-LUMO gap of the system is small, 20 | ||
- | ! points for the time/ | ||
- | ! (flag RPA_NUM_QUAD_POINTS). The time and frequency grid | ||
- | ! are equally large. The maximum grid size is 20. | ||
- | ! For large-gap systems (as the water molecule), 12 points | ||
- | ! should be sufficient | ||
- | RPA_NUM_QUAD_POINTS | ||
- | ! imaginary time flag enables cubic-scaling RPA or | ||
- | ! GW calculations | ||
- | IM_TIME | ||
- | & | ||
- | ! EPS_FILTER_IM_TIME should be tuned for the specific | ||
- | ! application: | ||
- | ! depends on EPS_FILTER | ||
- | EPS_FILTER_IM_TIME 1.0E-12 | ||
- | ! for large systems, increase GROUP_SIZE_3C | ||
- | ! to prevent out of memory (OOM) | ||
- | GROUP_SIZE_3C 1 | ||
- | ! for extremely large systems, increase GROUP_SIZE_P | ||
- | ! to prevent OOM | ||
- | ! for very large systems, it is also recommended | ||
- | ! to use OMP threads to prevent OOM | ||
- | GROUP_SIZE_P 1 | ||
- | ! for larger systems, MEMORY_CUT must be increased | ||
- | ! to prevent out of memory (OOM) | ||
- | MEMORY_CUT | ||
- | GW | ||
- | &END IM_TIME | ||
- | & | ||
- | | ||
- | | ||
- | | ||
- | | ||
- | | ||
- | | ||
- | &END RI_G0W0 | ||
- | &END RI_RPA | ||
- | &END | ||
- | &END XC | ||
- | &END DFT | ||
- | &SUBSYS | ||
- | &CELL | ||
- | ABC 10.0 10.0 10.0 | ||
- | PERIODIC NONE | ||
- | &END CELL | ||
- | &COORD | ||
- | O 0.0000 0.0000 0.0000 | ||
- | H 0.7571 0.0000 0.5861 | ||
- | H -0.7571 0.0000 0.5861 | ||
- | &END COORD | ||
- | & | ||
- | & | ||
- | &END | ||
- | &END TOPOLOGY | ||
- | &KIND H | ||
- | BASIS_SET def2-QZVP | ||
- | RI_AUX_BASIS RI-5Z | ||
- | POTENTIAL ALL | ||
- | &END KIND | ||
- | &KIND O | ||
- | BASIS_SET def2-QZVP | ||
- | RI_AUX_BASIS RI-5Z | ||
- | POTENTIAL ALL | ||
- | &END KIND | ||
- | &END SUBSYS | ||
- | &END FORCE_EVAL | ||
- | &GLOBAL | ||
- | RUN_TYPE | ||
- | PROJECT | ||
- | PRINT_LEVEL | ||
&END GLOBAL | &END GLOBAL | ||
</ | </ |
howto/gw.txt · Last modified: 2024/01/14 12:15 by oschuett