<div dir="ltr"><div><div><div>Matt,<br><br></div> Thanks for your clarification. I agree with you that the coupling term between occupied-virtual orbital pairs may deviate the excitation energy from HOMO-LUMO gap. I was just surprised by the rather large deviation on an isolated molecule which may stem from its small basis set as well as its small box size, as your suggested. I will make the system bigger with a larger basis set.<br><br></div>Best,<br><br></div>Hanning <br><div><div><div><br></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Feb 6, 2017 at 10:22 AM, Matt W <span dir="ltr"><<a href="mailto:MattWa...@gmail.com" target="_blank">MattWa...@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Hanning,<div><br></div><div>I've not had a chance to look at your particular calculation. Such a small basis set, and small box could lead to strange results in any case. More generally, there is no reason, even if the transition is a pure single determinant HOMO to LUMO, for the energy to be that of the HOMO_LUMO gap. There are still additional terms in the TDDFT kernel that will shift the transition energy.</div><div>For GGAs the shifts can be in either direction, there is no general rule.</div><div>We have checked small molecule transition energies vs gamess-us and were pretty happy with the comparison.</div><div><br></div><div>HTH,</div><div><br></div><div>Matt</div><div><div class="h5"><div><br></div><div><br>On Sunday, February 5, 2017 at 8:50:49 PM UTC, NUCP2K wrote:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Dear CP2K Developers and Users,<br><br> 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. <br><br> I tested the TDDFPT2 on an isolated water (H2O) molecule using the attached input file. Interestingly, the calculated excitation energy of 10.075 eV 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. <br><br> 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. <br><br> Please correct me if my understanding is wrong.<br><br> Thanks.<br><br>Hanning<br><br><br> &FORCE_EVAL<br> METHOD QS<br> &PROPERTIES<br> &TDDFPT<br> NSTATES 1<br> MAX_ITER 100<br> MAX_KV 10<br> CONVERGENCE [eV] 1.0E-3<br> &DIPOLE_MOMENTS<br> DIPOLE_FORM LENGTH<br> &END DIPOLE_MOMENTS<br> &MGRID<br> COMMENSURATE<br> CUTOFF 50<br> &END MGRID<br> &END TDDFPT<br> &END PROPERTIES<br> &DFT<br> BASIS_SET_FILE_NAME BASIS_SET<br> POTENTIAL_FILE_NAME POTENTIAL<br> &MGRID<br> COMMENSURATE<br> CUTOFF 50<br> &END MGRID<br> &POISSON<br> PERIODIC NONE<br> POISSON WAVELET<br> &END POISSON<br> &SCF<br> SCF_GUESS ATOMIC<br> &END SCF<br> &XC<br> &XC_FUNCTIONAL PBE<br> &END XC_FUNCTIONAL<br> &XC_GRID<br> XC_DERIV SPLINE2_SMOOTH<br> &END XC_GRID<br> &END XC<br> &END DFT<br> &SUBSYS<br> &CELL<br> ABC 6.0 6.0 6.0<br> PERIODIC NONE<br> &END CELL<br> &COORD<br> O 3.000000 3.000000 3.000000 H2O1<br> H 3.000000 3.000000 4.000000 H2O1<br> H 3.942809 3.000000 2.666667 H2O1<br> &END COORD<br> &KIND H<br> BASIS_SET SZV-GTH<br> POTENTIAL GTH-PADE-q1<br> &END KIND<br> &KIND O<br> BASIS_SET SZV-GTH<br> POTENTIAL GTH-PADE-q6<br> &END KIND<br> &TOPOLOGY<br> &END TOPOLOGY<br> &END SUBSYS<br>&END FORCE_EVAL<br>&GLOBAL<br> PROJECT WATER<br> PRINT_LEVEL MEDIUM<br> RUN_TYPE ENERGY<br>&END GLOBAL<br></div></blockquote></div></div></div></div><div class="HOEnZb"><div class="h5"> <p></p> -- <br> You received this message because you are subscribed to the Google Groups "cp2k" group.<br> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+uns...@googlegroups.com" target="_blank">cp2k+unsubscribe@googlegroups.<wbr>com</a>.<br> To post to this group, send email to <a href="mailto:cp...@googlegroups.com" target="_blank">cp...@googlegroups.com</a>.<br> Visit this group at <a href="https://groups.google.com/group/cp2k" target="_blank">https://groups.google.com/<wbr>group/cp2k</a>.<br> For more options, visit <a href="https://groups.google.com/d/optout" target="_blank">https://groups.google.com/d/<wbr>optout</a>.<br> </div></div></blockquote></div><br></div>