howto:xas_tdp
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howto:xas_tdp [2021/07/29 14:56] – [Simple examples] abussy | howto:xas_tdp [2021/08/02 15:40] – [FAQ] abussy | ||
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$$ | $$ | ||
- | where $\varepsilon_a$ is the orbital energy of a virtual MO and $\varepsilon_I$ the energy of the donor core MO. Under Koopman' | + | where $\varepsilon_a$ is the orbital energy of a virtual MO and $\varepsilon_I$ the energy of the donor core MO. Under Koopman' |
The IP can be accurately calculated using the second-order electron propagator equation: | The IP can be accurately calculated using the second-order electron propagator equation: | ||
Line 529: | Line 529: | ||
The parameters defining the GW2X correction to XAS LR-TDDFT are found in the '' | The parameters defining the GW2X correction to XAS LR-TDDFT are found in the '' | ||
+ | There are not many parameters to set for the GW2X correction. Simply adding an empty ''& | ||
==== Simple examples ==== | ==== Simple examples ==== | ||
- | === SO$_2$ | + | === OCS molecule (L-edge + SOC) === |
+ | |||
+ | This example covers GW2X corrected L-edge spectroscopy with spin-orbit coupling. | ||
+ | |||
+ | <code - OCS.inp> | ||
+ | |||
+ | & | ||
+ | PROJECT OCS | ||
+ | PRINT_LEVEL MEDIUM | ||
+ | RUN_TYPE ENERGY | ||
+ | &END GLOBAL | ||
+ | & | ||
+ | METHOD Quickstep | ||
+ | &DFT | ||
+ | BASIS_SET_FILE_NAME BASIS_GW2X | ||
+ | POTENTIAL_FILE_NAME POTENTIAL | ||
+ | AUTO_BASIS RI_XAS MEDIUM | ||
+ | |||
+ | & | ||
+ | CUTOFF 800 | ||
+ | REL_CUTOFF 50 | ||
+ | NGRIDS 5 | ||
+ | &END MGRID | ||
+ | &QS | ||
+ | METHOD GAPW | ||
+ | &END QS | ||
+ | |||
+ | & | ||
+ | PERIODIC NONE | ||
+ | PSOLVER MT | ||
+ | &END | ||
+ | |||
+ | &SCF | ||
+ | EPS_SCF 1.0E-8 | ||
+ | MAX_SCF 50 | ||
+ | &END SCF | ||
+ | |||
+ | &XC | ||
+ | & | ||
+ | & | ||
+ | FUNCTIONAL GGA_C_PBE | ||
+ | & | ||
+ | & | ||
+ | FUNCTIONAL GGA_X_PBE | ||
+ | SCALE 0.55 | ||
+ | & | ||
+ | &END XC_FUNCTIONAL | ||
+ | |||
+ | &HF | ||
+ | | ||
+ | &END HF | ||
+ | &END XC | ||
+ | |||
+ | & | ||
+ | & | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | &END DONOR_STATES | ||
+ | |||
+ | EXCITATIONS RCS_SINGLET | ||
+ | EXCITATIONS RCS_TRIPLET | ||
+ | SOC | ||
+ | |||
+ | GRID S 300 500 | ||
+ | |||
+ | N_EXCITED 150 | ||
+ | TAMM_DANCOFF | ||
+ | |||
+ | & | ||
+ | &END GW2X ! standard XAS_TDP calculation (defaults parameters are used) | ||
+ | |||
+ | & | ||
+ | | ||
+ | & | ||
+ | &LIBXC | ||
+ | | ||
+ | &END LIBXC | ||
+ | &LIBXC | ||
+ | | ||
+ | SCALE 0.55 | ||
+ | &END LIBXC | ||
+ | & | ||
+ | & | ||
+ | FRACTION 0.45 | ||
+ | & | ||
+ | &END KERNEL | ||
+ | |||
+ | &END XAS_TDP | ||
+ | &END DFT | ||
+ | & | ||
+ | &CELL | ||
+ | ABC 10.0 10.0 10.0 | ||
+ | PERIODIC NONE | ||
+ | &END CELL | ||
+ | & | ||
+ | C | ||
+ | O | ||
+ | S | ||
+ | &END COORD | ||
+ | &KIND C | ||
+ | BASIS_SET aug-pcX-2 | ||
+ | POTENTIAL ALL | ||
+ | &END KIND | ||
+ | &KIND O | ||
+ | BASIS_SET aug-pcX-2 | ||
+ | POTENTIAL ALL | ||
+ | &END KIND | ||
+ | &KIND S | ||
+ | BASIS_SET aug-pcX-2 | ||
+ | POTENTIAL ALL | ||
+ | &END KIND | ||
+ | &END SUBSYS | ||
+ | &END FORCE_EVAL | ||
+ | |||
+ | </ | ||
+ | |||
+ | The only difference between the above input file and that of a standard XAS LR-TDDFT calculation is the addition of the ''& | ||
+ | |||
+ | In the output file, the correction for each S $2p$ is displayed. Note that the correction amounts to a shift of 1.9 eV compared to standard XAS LR-TDDFT, leading to a first singlet excitation energy of 164.4 eV (at the L$_3$ edge). This fits [[https:// | ||
+ | |||
+ | < | ||
+ | - GW2X correction for donor MO with spin 1 and MO index 5: | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | |||
+ | Final GW2X shift for this donor MO (eV): | ||
+ | |||
+ | |||
+ | - GW2X correction for donor MO with spin 1 and MO index 6: | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | |||
+ | Final GW2X shift for this donor MO (eV): | ||
+ | |||
+ | |||
+ | - GW2X correction for donor MO with spin 1 and MO index 7: | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | |||
+ | Final GW2X shift for this donor MO (eV): | ||
+ | |||
+ | |||
+ | Calculations done: | ||
+ | |||
+ | First singlet XAS excitation energy (eV): 165.014087 | ||
+ | First triplet XAS excitation energy (eV): 164.681850 | ||
+ | First SOC XAS excitation energy (eV): 164.396537 | ||
+ | |||
+ | Ionization potentials for XPS (GW2X + SOC): 170.602279 | ||
+ | | ||
+ | | ||
+ | |||
+ | </ | ||
=== Solid NH$_3$ (K-edge, periodic) === | === Solid NH$_3$ (K-edge, periodic) === | ||
+ | |||
+ | This is a much larger example of a periodic system, namely solid ammonia. This example is much heavier to run (~45 minutes on 24 cores). | ||
+ | |||
+ | <code NH3.inp> | ||
+ | |||
+ | &GLOBAL | ||
+ | PROJECT NH3 | ||
+ | RUN_TYPE ENERGY | ||
+ | PRINT_LEVEL MEDIUM | ||
+ | &END GLOBAL | ||
+ | & | ||
+ | METHOD QS | ||
+ | &DFT | ||
+ | BASIS_SET_FILE_NAME BASIS_GW2X | ||
+ | BASIS_SET_FILE_NAME BASIS_ADMM | ||
+ | BASIS_SET_FILE_NAME BASIS_MOLOPT | ||
+ | POTENTIAL_FILE_NAME POTENTIAL | ||
+ | AUTO_BASIS RI_XAS MEDIUM | ||
+ | |||
+ | &QS | ||
+ | METHOD GAPW | ||
+ | &END QS | ||
+ | |||
+ | &MGRID | ||
+ | CUTOFF 600 | ||
+ | REL_CUTOFF 50 | ||
+ | NGRIDS 5 | ||
+ | &END MGRID | ||
+ | |||
+ | &SCF | ||
+ | SCF_GUESS RESTART | ||
+ | EPS_SCF 1.0E-8 | ||
+ | MAX_SCF 30 | ||
+ | |||
+ | &OT | ||
+ | | ||
+ | | ||
+ | &END OT | ||
+ | |||
+ | & | ||
+ | | ||
+ | | ||
+ | &END OUTER_SCF | ||
+ | |||
+ | &END SCF | ||
+ | |||
+ | & | ||
+ | ADMM_PURIFICATION_METHOD NONE | ||
+ | &END AUXILIARY_DENSITY_MATRIX_METHOD | ||
+ | |||
+ | &XC | ||
+ | & | ||
+ | & | ||
+ | FUNCTIONAL GGA_X_PBE | ||
+ | SCALE 0.55 | ||
+ | & | ||
+ | & | ||
+ | FUNCTIONAL GGA_C_PBE | ||
+ | & | ||
+ | &END XC_FUNCTIONAL | ||
+ | &HF | ||
+ | | ||
+ | & | ||
+ | POTENTIAL_TYPE TRUNCATED | ||
+ | CUTOFF_RADIUS 5.0 | ||
+ | & | ||
+ | &END HF | ||
+ | &END XC | ||
+ | |||
+ | & | ||
+ | & | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | &END DONOR_STATES | ||
+ | |||
+ | TAMM_DANCOFF | ||
+ | GRID Nx 300 500 | ||
+ | E_RANGE 30.0 | ||
+ | |||
+ | &GW2X | ||
+ | &END | ||
+ | |||
+ | &KERNEL | ||
+ | & | ||
+ | &LIBXC | ||
+ | | ||
+ | SCALE 0.55 | ||
+ | &END | ||
+ | &LIBXC | ||
+ | | ||
+ | &END | ||
+ | & | ||
+ | & | ||
+ | OPERATOR TRUNCATED | ||
+ | CUTOFF_RADIUS 5.0 | ||
+ | FRACTION 0.45 | ||
+ | & | ||
+ | &END KERNEL | ||
+ | |||
+ | &END XAS_TDP | ||
+ | &END DFT | ||
+ | &SUBSYS | ||
+ | &CELL | ||
+ | ABC | ||
+ | &END CELL | ||
+ | & | ||
+ | COORD_FILE_FORMAT XYZ | ||
+ | COORD_FILE_NAME NH3.xyz | ||
+ | &END TOPOLOGY | ||
+ | &KIND H | ||
+ | BASIS_SET DZVP-MOLOPT-SR-GTH | ||
+ | BASIS_SET AUX_FIT FIT3 | ||
+ | POTENTIAL GTH-PBE | ||
+ | &END KIND | ||
+ | &KIND N | ||
+ | BASIS_SET DZVP-MOLOPT-SR-GTH | ||
+ | BASIS_SET AUX_FIT FIT3 | ||
+ | POTENTIAL GTH-PBE | ||
+ | &END KIND | ||
+ | &KIND Nx | ||
+ | ELEMENT N | ||
+ | BASIS_SET aug-pcseg-2 | ||
+ | BASIS_SET AUX_FIT aug-admm-2 | ||
+ | POTENTIAL ALL | ||
+ | &END KIND | ||
+ | &END SUBSYS | ||
+ | &END FORCE_EVAL | ||
+ | |||
+ | </ | ||
+ | |||
+ | Again, the only difference with respect to a standard XAS-LRTDDFT input file is the ''& | ||
+ | |||
==== FAQ ==== | ==== FAQ ==== | ||
=== How can I make the GW2X correction run faster ?=== | === How can I make the GW2X correction run faster ?=== | ||
+ | |||
+ | The GW2X correction scheme scales cubically with the number of MOs in the system. Therefore, the best way to improve performance is to reduce that number. Because an accurate description of the core region is only necessary for the exited atoms, all other atoms can be described with pseudopotentials. This drastically reduces the number of MOs since only valence states are kept. In the solid NH3 example above, all nitrogen atoms are equivalent under symmetry. Therefore, their individual contribution to the XAS spectrum is bound to be the same. This allows for the description of a single nitrogen atom at the all-electron level, while all others (and the hydrogens) use pseudopotentials. Note that the ADMM approximation is also utilized. This greatly reduces the cost of the underlying hybrid DFT calculation, | ||
=== Why don't I get the absolute core IP in periodic systems ? === | === Why don't I get the absolute core IP in periodic systems ? === | ||
+ | |||
+ | For molecules in non-periodic boundary conditions, the potential is such that it is zero far away. In the periodic case, the zero is ill defined. As a consequence, | ||
+ | |||
+ | === Why is the LOCALIZE keyword required ? === | ||
+ | In order to efficiently evaluate the antisymmetric integrals of the type $\langle Ia || jk \rangle$, the same local RI scheme as XAS_TDP is used. Therefore, the core state $I$ needs to be local in space. However, the rotation required to get the pseudocanonical orbitals needed for the original GW2X scheme may break this localization, |
howto/xas_tdp.txt · Last modified: 2024/02/24 10:01 by oschuett