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

------=_NextPart_000_0048_01D1A7D4.F4680C60-- From owner-chemistry@ccl.net Sat May 7 13:07:01 2016 From: "Robert Molt r.molt.chemical.physics . gmail.com" To: CCL Subject: CCL: excited state calculations Message-Id: <-52180-160507112800-11559-mfz0FcwEvghhJ6438YYXrw(a)server.ccl.net> X-Original-From: Robert Molt Content-Type: multipart/alternative; boundary="------------090601010200010203050308" Date: Sat, 7 May 2016 16:27:53 +0100 MIME-Version: 1.0 Sent to CCL by: Robert Molt [r.molt.chemical.physics:_:gmail.com] This is a multi-part message in MIME format. --------------090601010200010203050308 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 1.) Yes, diffuse functions are essential in describing excited states. However, it's not just Rydberg states; even valence states quantitatively need the diffuse functions or they can be off 0.3eV, easily, purely as a basis set error (let alone the error of the many-body method). The Rydberg states you just might miss entirely (won't be there). Which is not to say you necessarily need as many diffuse functions as are in aug-cc-pVTZ; you could possibly get away with less (as long as you have some). 2.) Your oscillator strengths should either sum to one or the number of particles (there are two conventions for normalization of the matrix elements in oscillator strengths). What software are you using? On 5/7/16 2:22 AM, Michael Morgan michaelmorgan937-x-gmail.com wrote: > > 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 > 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}=1 and \sigma_{ij} f_{ij}=N > (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 > --------------090601010200010203050308 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit 1.) Yes, diffuse functions are essential in describing excited states.

However, it's not just Rydberg states; even valence states quantitatively need the diffuse functions or they can be off 0.3eV, easily, purely as a basis set error (let alone the error of the many-body method). The Rydberg states you just might miss entirely (won't be there).

Which is not to say you necessarily need as many diffuse functions as are in aug-cc-pVTZ; you could possibly get away with less (as long as you have some).

2.) Your oscillator strengths should either sum to one or the number of particles (there are two conventions for normalization of the matrix elements in oscillator strengths). What software are you using?

On 5/7/16 2:22 AM, Michael Morgan michaelmorgan937-x-gmail.com wrote:

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 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}=1 and \sigma_{ij} f_{ij}=N (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

--------------090601010200010203050308-- From owner-chemistry@ccl.net Sat May 7 17:32:01 2016 From: "Daniel Salazar danielmoralessalazar91:+:gmail.com" To: CCL Subject: CCL:G: About phosphorus-carbon double bond vibrational-frequency(ies) Message-Id: <-52181-160507150324-22584-Z/OX3IvkYa5EYBpXNkp80Q=server.ccl.net> X-Original-From: "Daniel Salazar" Date: Sat, 7 May 2016 15:03:23 -0400 Sent to CCL by: "Daniel Salazar" [danielmoralessalazar91]=[gmail.com] Hello, I am using B3LYP on Gaussian 09. I used it to obtain the vibrational frequencies of a molecule (C39H41PS2) containing one phosphorus carbon double bond by using the keyword "freq". I used Molden to visualize the calculated IR Spectrum. Since there are a lot of frequencies and the phosphorus carbon double bond may have a low intensity, I am having a hard time finding its frequency on the "Molden Frequency Select" panel. I wonder if there is any way to obtain this information in other ways, such as from the text output file, and if there is, how can I do it? Thank you very much. Sincerely, Daniel Morales Salazar