dft scf convergence problem

Viewed 888 times, With a total of 1 Posts

 Guest - Send PM
 2:23:22 PM PDT - Sat, Jun 25th 2011 Dear nwchem community, I am having trouble to convergence a wavefunction for a carbon nanotube with 2 hydrogen atoms using DFT+PBE0. Here is (part of) the input ```basis * library 3-21g end dft iterations 2000 xc pbe0 direct grid fine convergence gradient 8E-4 diis 4 end driver xyz geo end task dft optimize``` I have two systems (quite similar except for different positioning of the hydrogen atoms. The structures are optimized PBE geometries from CPMD. Here is one that works ```2b/output: d= 0,ls=0.0,diis 1 -9108.4700250578 -8.16D+04 8.10D+00 2.44D+01 5609.3 2b/output: d= 0,ls=0.5,diis 2 -9034.9757357418 7.35D+01 4.66D-01 8.74D+01 17541.8 2b/output: d= 0,ls=0.5,diis 3 -9041.3269753269 -6.35D+00 2.02D-01 7.76D+01 29413.3 2b/output: d= 0,ls=0.5,diis 4 -9043.6904442580 -2.36D+00 1.21D-01 7.56D+01 41248.0 2b/output: d= 0,ls=0.5,diis 5 -9044.9817332625 -1.29D+00 7.70D+00 7.43D+01 53002.8 2b/output: d= 0,ls=0.5,diis 6 -9095.2034257819 -5.02D+01 3.46D-02 5.85D+01 59436.9 2b/output: d= 0,ls=0.5,diis 7 -9105.7684680531 -1.06D+01 4.17D-03 1.89D+01 65563.8 2b/output: d= 0,ls=0.5,diis 8 -9104.4813523533 1.29D+00 1.18D-03 3.24D+01 71684.0 2b/output: d= 0,ls=0.5,diis 9 -9105.8769727898 -1.40D+00 7.15D-04 2.18D+01 77663.8 2b/output: d= 0,ls=0.5,diis 10 -9107.4244567859 -1.55D+00 1.16D-03 1.31D+01 83650.6 2b/output: d= 0,ls=0.5,diis 11 -9109.2070951994 -1.78D+00 1.27D-03 4.41D+00 92383.6 2b/output: d= 0,ls=0.5,diis 12 -9110.2622692031 -1.06D+00 5.06D-04 6.65D-01100948.2 2b/output: d= 0,ls=0.5,diis 13 -9110.3633724795 -1.01D-01 2.90D-04 3.92D-01108950.1 2b/output: d= 0,ls=0.5,diis 14 -9110.4234724909 -6.01D-02 2.45D-04 2.25D-01114918.9 2b/output: d= 0,ls=0.5,diis 15 -9110.4774325073 -5.40D-02 1.56D-04 6.57D-02120876.2 2b/output: d= 0,ls=0.5,diis 16 -9110.5041094244 -2.67D-02 1.04D-04 2.15D-02126837.3 2b/output: d= 0,ls=0.5,diis 17 -9110.5187859539 -1.47D-02 9.39D-05 1.60D-02132823.1 2b/output: d= 0,ls=0.5,diis 18 -9110.5298692886 -1.11D-02 9.20D-05 1.29D-02138816.4 2b/output: d= 0,ls=0.5,diis 19 -9110.5394020628 -9.53D-03 7.53D-05 9.69D-03144784.6 2b/output: d= 0,ls=0.5,diis 20 -9110.5469022106 -7.50D-03 6.75D-05 7.56D-03150754.4``` And one that doesn't ```2a/output: d= 0,ls=0.0,diis 1 -9108.5023183806 -8.16D+04 8.27D+00 2.43D+01 5616.0 2a/output: d= 0,ls=0.5,diis 2 -9034.6634884197 7.38D+01 4.65D-01 8.50D+01 17581.9 2a/output: d= 0,ls=0.5,diis 3 -9040.9435208185 -6.28D+00 1.96D-01 7.60D+01 29477.9 2a/output: d= 0,ls=0.5,diis 4 -9043.2585279689 -2.32D+00 1.22D-01 7.42D+01 41316.6 2a/output: d= 0,ls=0.5,diis 5 -9044.5516229056 -1.29D+00 7.86D+00 7.31D+01 53169.2 2a/output: d= 0,ls=0.5,diis 6 -9093.4199801709 -4.89D+01 2.87D-02 6.70D+01 59590.5 2a/output: d= 0,ls=0.5,diis 7 -9080.1167325488 1.33D+01 3.59D-03 1.43D+02 65637.3 2a/output: d= 0,ls=0.5,diis 8 -9095.7736875505 -1.57D+01 1.38D-03 6.66D+01 71659.0 2a/output: d= 0,ls=0.5,diis 9 -9099.3601973387 -3.59D+00 7.82D-04 4.62D+01 77709.0 2a/output: d= 0,ls=0.5,diis 10 -9102.5658530250 -3.21D+00 1.79D-02 3.06D+01 83711.3 2a/output: d= 0,ls=0.5,diis 11 -9030.5701065372 7.20D+01 4.80D-03 3.48D+02 93114.0 2a/output: d= 0,ls=0.5,diis 12 -9035.9333262450 -5.36D+00 3.85D-03 2.94D+02102218.4 2a/output: d= 0,ls=0.5,diis 13 -9039.6119263338 -3.68D+00 3.68D-03 2.71D+02110320.0 2a/output: d= 0,ls=0.5,diis 14 -9042.2300588374 -2.62D+00 1.59D-01 2.66D+02116583.4 2a/output: d= 0,ls=0.5,diis 15 -942.0039711970 8.10D+03 7.09D-02 1.99D+04123442.3 2a/output: d= 0,ls=0.5,diis 16 -3417.0117307364 -2.48D+03 4.12D-02 1.52D+04130265.1 2a/output: d= 0,ls=0.5,diis 17 -4366.1889341364 -9.49D+02 3.40D-02 1.61D+04137121.0 2a/output: d= 0,ls=0.5,diis 18 -4847.9189437237 -4.82D+02 5.71D+00 1.96D+04144007.5 2a/output: d= 0,ls=0.5,diis 19 43359.2082533070 4.82D+04 7.22D+00 3.62D+03152453.2 2a/output: d= 0,ls=0.5,diis 20 35898.8558078528 -7.46D+03 4.11D+00 1.53D+04160518.8 2a/output: d= 0,ls=0.5,diis 21 24338.8539746737 -1.16D+04 4.64D-01 2.30D+04167974.2 2a/output: d= 0,ls=0.5,diis 22 22345.8899119936 -1.99D+03 6.14D-01 2.31D+04175136.6``` It seems to me that the initial step size is too large and the DIIS algorithm gets lost for the latter geometry. Is there a way to choose the initial DIIS step size? Or is there another, algorithm like steepest descent or conjugate gradient that I can try for the SCF convergence? (I could not find it in the part of manual about dft) Thank you in advance for any suggestions. Best, Jaap

 Niri Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop Profile Send PM
 Gets Around Threads 4 Posts 104
 2:36:30 PM PDT - Mon, Jun 27th 2011 Hi Jaap, We are aware of the convergence issues with the standard diis. I will be releasing a quadratic convergence algorithm as soon as I tie up some loose ends. In the meantime the following modified input should help convergence. Here's the modified input. This will do a HF calculation and then use these vectors as input for the PBE0 basis ```* library 3-21g ``` end scf ``` maxiter 100 direct vectors output hf.movecs ``` end task scf energy dft ``` iterations 2000 xc pbe0 direct grid fine vectors input hf.movecs output pbe0.movecs ``` end driver ``` xyz geo ``` end task dft optimize Let me know if there are further issues. Best wishes, -Niri

 Who's here now Members 0 Guests 1 Bots/Crawler 0

AWC's: 2.5.10 MediaWiki - Stand Alone Forum Extension
Forum theme style by: AWC