<div dir="ltr">Dear CP2K Developers and Users, Â I just tried out the latest implementation of time-dependent density functional perturbation theory (TDDFPT) in CP2K, and found some serious inconsistencies on the calculated excitation energy. Â I tested the TDDFPT2 on an isolated water (H2O) molecule using the attached input file. Interestingly, the calculated excitation energy of 10.075 eVÂ is much much greater than the HOMO-LUMO gap of 9.137 eV, even though the transition is dominated (>99.9%) by the electron transfer from HOMO to LUMO.Â Â It seems to me that the diagonal terms of the TDDFPT response matrix are not appropriately assigned, leading to the apparent inconsistency. Perhaps, the subroutine "tddfpt_init_by_energy_diff" in qs_tddfpt2_methods.F should be fixed to yield correct orbital energy gap. Â Please correct me if my understanding is wrong. Â Thanks. Hanning Â Â Â Â Â Â Â Â &FORCE_EVAL Â METHOD QS Â &PROPERTIES Â Â Â &TDDFPT Â Â Â Â NSTATESÂ Â Â Â Â 1 Â Â Â Â MAX_ITERÂ Â Â 100 Â Â Â Â MAX_KV 10 Â Â Â Â CONVERGENCE [eV] 1.0E-3 Â Â Â Â &DIPOLE_MOMENTS Â Â Â Â Â DIPOLE_FORM LENGTH Â Â Â Â &END DIPOLE_MOMENTS Â Â Â Â &MGRID Â Â Â Â Â COMMENSURATE Â Â Â Â Â CUTOFF 50 Â Â Â Â &END MGRID Â Â Â &END TDDFPT Â &END PROPERTIES Â &DFT Â Â Â BASIS_SET_FILE_NAME BASIS_SET Â Â Â POTENTIAL_FILE_NAME POTENTIAL Â Â Â &MGRID Â Â Â Â Â COMMENSURATE Â Â Â Â Â CUTOFF 50 Â Â Â &END MGRID Â Â Â &POISSON Â Â Â Â PERIODIC NONE Â Â Â Â POISSON WAVELET Â Â Â &END POISSON Â Â Â &SCF Â Â Â Â Â SCF_GUESS ATOMIC Â Â Â &END SCF Â Â Â &XC Â Â Â Â Â &XC_FUNCTIONAL PBE Â Â Â Â Â &END XC_FUNCTIONAL Â Â Â Â Â &XC_GRID Â Â Â Â Â Â Â XC_DERIV SPLINE2_SMOOTH Â Â Â Â Â &END XC_GRID Â Â Â &END XC Â &END DFT Â &SUBSYS Â Â Â &CELL Â Â Â Â Â ABC 6.0 6.0 6.0 Â Â Â Â Â PERIODIC NONE Â Â Â &END CELL Â Â Â &COORD Â Â OÂ Â Â Â 3.000000Â Â Â Â 3.000000Â Â Â Â 3.000000Â Â Â H2O1 Â Â HÂ Â Â Â 3.000000Â Â Â Â 3.000000Â Â Â Â 4.000000Â Â Â H2O1 Â Â HÂ Â Â Â 3.942809Â Â Â Â 3.000000Â Â Â Â 2.666667Â Â Â H2O1 Â Â Â &END COORD Â Â Â &KIND H Â Â Â Â Â BASIS_SET SZV-GTH Â Â Â Â Â POTENTIAL GTH-PADE-q1 Â Â Â &END KIND Â Â Â &KIND O Â Â Â Â Â BASIS_SET SZV-GTH Â Â Â Â Â POTENTIAL GTH-PADE-q6 Â Â Â &END KIND Â Â Â &TOPOLOGY Â Â Â &END TOPOLOGY Â &END SUBSYS &END FORCE_EVAL &GLOBAL Â PROJECT WATER Â PRINT_LEVEL MEDIUM Â RUN_TYPE ENERGY &END GLOBAL </div>