Dear Eli:<= /span>

It is widely accepted = that TDDFT works bad for conjugate systems, especially for large ones.

But this does not mean that TDDFT is a bad one. In fact= , it is a routinely applied method and

for most case= s it can give a qualitatively correct result, except for cases such as char= ge transfer

excitation, Rydberg states, and large c= onjugate molecules metioned above.

TDHF, whose was called RPA in the past, is somewhat old and l= ess used. But, you can perform a

benchmark calculat= ion for your own system with TDDFT, TDHF with different basis sets, and

decide witch model is the most suitable for your system.

Best regards!=

----------------------------------------------------------------
Jun = Zhang (coolrainbow-#-yahoo.cn)
Computational Chemistry Group
No.94, Wei= jinlu
Nankai University
Tianjin, China

=E5=8F=91=E4=BB=B6=E4=BA=BA= =EF=BC=9A Eli Lam elizabeth.shlam(~)gmail.com <owner-chemistr= y-#-ccl.net>
=E6=94=B6=E4=BB=B6= =E4=BA=BA=EF=BC=9A "Zhang, Jun " <coolrainbow-#-yahoo.cn>
= =E5=8F=91=E9=80=81=E6=97=A5=E6=9C=9F=EF=BC=9A 2011=E5=B9=B411=E6= =9C=8820=E6=97=A5, =E6=98=9F=E6=9C=9F=E6=97=A5, =E4=B8=8A=E5=8D=88 8:40
= =E4=B8=BB=E9=A2=98: CCL: = Tddft and tdhf accuracy

Sent to CCL by: "Eli Lam"= [elizabeth.shlam-*-gmail.com]
Dear all,

I've learnt that tddft a= nd tdhf both are methods for calculating excited states and electronic
= transitions. I would like to ask which method is more accurate and gi= ve a "better" picture to an
organometallic molecule's excited state, fo= r example?

I have learnt that tddft is not good for high exci= ted states calculations but generally good for
radicals. But woul= d it be good for neutral molecules too? And in particular, I found td= dft seems
to have underestimated much for very conjugated systems. A fr= iend said it's because tddft is
based on ground state, and for excited = states, hf does a better job. I would like to ask for more
views on that.&n= bsp; And would you please suggest some readings concerning the issue? = Thanks so
much!

Regards,
Eli

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=

IHello... I heard from the late Michael Zerner, author of the semiempirical ZINDO code, "Nothing is so semiempirical as an ab initio calculation." = ... meaning that all methods have to be calibrated. My experience with hunderds TDDFT calculations and thousands of TDHF/RPA INDO/S calculations = is consistent with this. John McKelvey

Sent to CCL by: "Eli Lam" [elizabeth.shlam-*-gmail.com] Dear all, I've learnt that tddft and tdhf both are methods for calculating excited states and electronic transitions. I would like to ask which method is more accurate and give a "better" picture to an organometallic molecule's excited state, for example? I have learnt that tddft is not good for high excited states calculations but generally good for radicals. But would it be good for neutral molecules too? And in particular, I found tddft seems to have underestimated much for very conjugated systems. A friend said it's because tddft is based on ground state, and for excited states, hf does a better job. I would like to ask for more views on that. And would you please suggest some readings concerning the issue? Thanks so much! Regards, EliE-mail to subscribers: CHEMISTRY||ccl.net or use: http://www.ccl.net/cgi-bin/ccl/send_ccl_message E-mail to administrators: CHEMISTRY-REQUEST||ccl.net or use http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtml Before posting, check wait time at: http://www.ccl.net Job: http://www.ccl.net/jobs Conferences: http://server.ccl.net/chemistry/announcements/conferences/ Search Messages: http://www.ccl.net/chemistry/searchccl/index.shtmlhttp://www.ccl.net/spammers.txt RTFI: http://www.ccl.net/chemistry/aboutccl/instructions/