From owner-chemistry@ccl.net Sun Nov 27 19:48:01 2011 From: "Josh Marell mare0051(a)umn.edu" To: CCL Subject: CCL: Convergence During Frequency Analysis Message-Id: <-45930-111127192934-28069-66xJgG2CraHJ45FhYyoAqg!=!server.ccl.net> X-Original-From: Josh Marell Content-Type: multipart/alternative; boundary=20cf300e568b4889f804b2c098bc Date: Sun, 27 Nov 2011 18:29:04 -0600 MIME-Version: 1.0 Sent to CCL by: Josh Marell [mare0051 * umn.edu] --20cf300e568b4889f804b2c098bc Content-Type: text/plain; charset=ISO-8859-1 Hi Cina, Thank you for the response. I rechecked the calculations, and have switched to instead doing an initial optimization with opt=caclfc (to get closer to the real minimum), and then a second step of opt=calcall, which usually finishes in just one or two extra optimization steps along with the frequency analysis output. Thanks for the assistance, Josh On Sun, Nov 13, 2011 at 11:52 PM, cina foroutan canyslopus|yahoo.co.uk < owner-chemistry,,ccl.net> wrote: > Dear Josh, > > I have had this problem many times before. This tells that your geometry > does not correspond to the real local minimum. To check it you can submit a > new optimization with your optimized geometry and consider opt=readfc > guess=read keywords (please note that if you saved a chk file you can use > these keywords!). If your structure is the real minimum, the new job must > finishes after just one cycle. However, I guess that, this is not the case > for you. > To get the real minimum on the PES you may also consider opt=(calcall). > Then, the second derivatives of energy will be computed in every step of > optimization and you can be sure that you will find the real local minimum. > Unfortunately, calcall keyword is very demanding because as I mentioned in > every step of the optimization second derivatives of energy must be > computed, this means that every optimization step is as demanding as a > frequency calculation. > > Good luck > Cina Foroutan-Nejad > > ------------------------------ > *From:* Josh Marell mare0051-#-umn.edu > *To:* "Foroutan-Nejad, Cina " > *Sent:* Monday, 14 November 2011, 1:33 > *Subject:* CCL: Convergence During Frequency Analysis > > Hello, > > I am optimizing a geometry at the m062x/6-31+g(d,p) level, and then I > perform a frequency analysis. During the optimization step (and utilizing > opt=verytight), I ensure that I am getting full convergence and see: > > Maximum Force 0.000000 0.000002 YES > RMS Force 0.000000 0.000001 YES > Maximum Displacement 0.000005 0.000006 YES > RMS Displacement 0.000001 0.000004 YES > > However, then I carry out a frequency analysis using the following route > section: > # m062x/6-31+g(d,p) freq integral(ultrafinegrid) scrf=check geom=checkpoint > > And at the end of the output file for the frequency analysis, it indicates > in this specific case that none of the criteria have converged (this is > after the line that specifies the axes has been restored to the original > set) > > Item Value Threshold Converged? > Maximum Force 0.024599 0.000450 NO > RMS Force 0.005725 0.000300 NO > Maximum Displacement 0.311758 0.001800 NO > RMS Displacement 0.083739 0.001200 NO > Predicted change in Energy=-4.741844D-03 > GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad > > Is this telling me the results of the frequency analysis are not reliable? > I guess I'm unclear why the geometry that converged with verytight > requirement is now not converging during the frequency job (assuming I'm > understanding the implication of the above correctly). > > Thank you, > > Josh > > > --20cf300e568b4889f804b2c098bc Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Cina,

Thank you for the response. =A0I rechecked the = calculations, and have switched to instead doing an initial optimization wi= th opt=3Dcaclfc (to get closer to the real minimum), and then a second step= of opt=3Dcalcall, which usually finishes in just one or two extra optimiza= tion steps along with the frequency analysis output.

Thanks for the assistance,

Jos= h

On Sun, Nov 13, 2011 at 11:52 PM, cina foroutan = canyslopus|yahoo.co.uk <owner-chemistry,,ccl.net= > wrote:
Dear Josh,

I = have had this problem many times before. This tells that your geometry does= not correspond to the real local minimum. To check it you can submit a new= optimization with your optimized geometry and consider opt=3Dreadfc guess= =3Dread keywords (please note that if you saved a chk file you can use thes= e keywords!). If your structure is the real minimum, the new job must finis= hes after just one cycle. However, I guess that, this is not the case for y= ou.
To get the real minimum on the PES you may also consider opt=3D(= calcall). Then, the second derivatives of energy will be computed in every = step of optimization and you can be sure that you will find the real local = minimum. Unfortunately, calcall keyword is very demanding because as I ment= ioned in every step of the optimization second derivatives of energy must be com= puted, this means that every optimization step is as demanding as a frequen= cy calculation.

Good luc= k
Cina Foroutan-Nejad

From: Josh Marell mare0051-#-umn.edu <owner-chemistry{}ccl.net>
To: "Foroutan-Nejad, Ci= na " <canyslopus{}= yahoo.co.uk>
Sent:= Monday, 14 November 2011, 1:33
Subject: CCL: Convergence Du= ring Frequency Analysis

Hello,

I = am optimizing a geometry at the m062x/6-31+g(d,p) level, and then I perform= a frequency analysis. =A0During the optimization step (and utilizing opt= =3Dverytight), I ensure that I am getting full convergence and see:

Maximum Force =A0 =A0 =A0 =A0 =A0 =A00.000000 =A0 = =A0 0.000002 =A0 =A0 YES
=A0RMS =A0 =A0 Force =A0 =A0 =A0 =A0 =A0= =A00.000000 =A0 =A0 0.000001 =A0 =A0 YES
=A0Maximum Displacement= =A0 =A0 0.000005 =A0 =A0 0.000006 =A0 =A0 YES
=A0RMS =A0 =A0 Displacement =A0 =A0 0.000001 =A0 =A0 0.000004 =A0 =A0 YES

However, then I carry out a frequency analysi= s using the following route section:
# m062x/6-31+g(d,p) freq int= egral(ultrafinegrid) scrf=3Dcheck geom=3Dcheckpoint

And at the end of the output file for the frequency ana= lysis, it indicates in this specific case that none of the criteria have co= nverged (this is after the line that specifies the axes has been restored t= o the original set)

=A0 =A0 =A0 =A0 =A0Item =A0 =A0 =A0 =A0 =A0 =A0 = =A0 Value =A0 =A0 Threshold =A0Converged?
=A0Maximum Force =A0 =A0 =A0 =A0 =A0 =A00.024599 =A0 =A0 0.000450 =A0 = =A0 NO=A0
=A0RMS =A0 =A0 Force =A0 =A0 =A0 =A0 =A0 =A00.005725 = =A0 =A0 0.000300 =A0 =A0 NO=A0
=A0Maximum Displacement =A0 =A0 0.= 311758 =A0 =A0 0.001800 =A0 =A0 NO=A0
=A0RMS =A0 =A0 Displacement= =A0 =A0 0.083739 =A0 =A0 0.001200 =A0 =A0 NO=A0
=A0Predicted change in Energy=3D-4.741844D-03
=A0GradGradGra= dGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad

Is this telling me the results of the frequency ana= lysis are not reliable? =A0I guess I'm unclear why the geometry that co= nverged with verytight requirement is now not converging during the frequen= cy job (assuming I'm understanding the implication of the above correct= ly).

Thank you,

Josh



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