From owner-chemistry@ccl.net Sat May 7 02:43:01 2016 From: "Michael Morgan michaelmorgan937-x-gmail.com" To: CCL Subject: CCL: excited state calculations Message-Id: <-52179-160506212233-23839-cIJXanajna8XTEPZRTYTjQ]=[server.ccl.net> X-Original-From: "Michael Morgan" Content-Language: en-us Content-Type: multipart/alternative; boundary="----=_NextPart_000_0048_01D1A7D4.F4680C60" Date: Fri, 6 May 2016 20:22:04 -0500 MIME-Version: 1.0 Sent to CCL by: "Michael Morgan" [michaelmorgan937()gmail.com] This is a multipart message in MIME format. ------=_NextPart_000_0048_01D1A7D4.F4680C60 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Dear all, =20 I am recently learning excited state calculations (TDDFT or EOM-CC). = When I compared the results using basis sets cc-pvtz or aug-cc-pvtz, I = have following observations (excitation energies were always calculated = up to 9.92eV, which is the limit I can reach experimentally using vacuum = uv): =20 1) with aug-cc-pvtz, more excitations (for transitions <9.92eV) were = found.=20 =20 > From what I read the reason seems to be that a lot of Rydberg transition = can only be found with diffuse functions. So a lot of Rydberg = transitions are missing when using cc-pvtz. Is this explanation correct? =20 2) with aug-cc-pvtz, the total sum of oscillator strengths (for all = transitions <9.92eV) increase significantly as well. =20 There is sum rule that \sigma_j f_{ij}=3D1 and \sigma_{ij} f_{ij}=3DN = (total number of electrons). Ideally if all transitions were found, sum = of f should be the same. So I think if the number of transitions is big = enough, the sum of f should tend to be the same. For many molecules I = calculated, the number of transitions is several hundred. So why the sum = of f with aug-cc-pvtz is always much bigger than the one with cc-pvtz? I = am interested in this question because I want to correlate the total = oscillator strength to experimental total response from vacuum uv, but I = not sure which calculated results I should trust more. =20 Thank you very much! M.M =20 =20 =20 =20 =20 ------=_NextPart_000_0048_01D1A7D4.F4680C60 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Dear all,

 

I am recently learning excited state calculations (TDDFT or EOM-CC). = When I compared the results using basis sets cc-pvtz or aug-cc-pvtz, I = have following observations (excitation energies were always=C2=A0 = calculated up to 9.92eV, which is the limit I can reach experimentally = using vacuum uv):

 

1) with aug-cc-pvtz, more excitations (for transitions <9.92eV) were = found.

 

From what I read the reason seems to be that a lot of Rydberg = transition can only be found with diffuse functions. So a lot of Rydberg = transitions are missing when using cc-pvtz. Is this explanation = correct?

 

2) with aug-cc-pvtz, the total sum of oscillator strengths (for all = transitions <9.92eV) increase significantly as = well.

 

There is sum rule that \sigma_j f_{ij}=3D1 and \sigma_{ij} f_{ij}=3DN = (total number of electrons). Ideally if all transitions were found, sum = of f should be the same. So I think if the number of transitions is big = enough, the sum of f should tend to be the same. For many molecules I = calculated, the number of transitions is several hundred. So why the sum = of f with aug-cc-pvtz is always much bigger than the one with cc-pvtz? I = am interested in this question because I want to correlate the total = oscillator strength to experimental total response from vacuum uv, but I = not sure which calculated results I should trust = more.

 

Thank you very much!

M.M

 

 

 

 

 

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