QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: baizq on February 29, 2016, 06:02

Title: Estimate the convergence of NEB
Post by: baizq on February 29, 2016, 06:02: I have very limited experience with NEB calculation. Just would like to know how one usually estimate (based on the runtime output) whether a NEB will achieve convergence or not. For example, if the output is as follows, should we expect a convergence or just give up?

| NEB Optimization using the LBFGS optimizer |
+------------------------------------------------------------------------------+
| Iteration Step Length Max. Force Max. Energy Image Max. Energy |
+------------------------------------------------------------------------------+
| 0 0.000e+00 8.290e+00 3 4.074025 |
| 1 1.677e-01 1.750e+00 3 2.338270 |
| 2 5.741e-02 1.806e+00 3 2.006154 |
| 3 7.919e-02 1.724e+00 3 1.740350 |
| 4 1.725e-01 1.884e+00 4 1.449709 |
| 5 1.772e-01 2.875e+00 3 1.344200 |
| 6 9.295e-02 1.463e+00 4 1.175542 |
| 7 1.124e-01 1.656e+00 4 1.041492 |
| 8 1.060e-01 1.814e+00 3 0.952107 |
| 9 8.552e-02 1.329e+00 3 0.839494 |
| 10 5.592e-02 2.038e+00 4 0.849147 |
| 11 4.137e-02 9.464e-01 4 0.726946 |
| 12 1.717e-01 2.818e+00 5 0.636764 |
| 13 6.338e-02 1.331e+00 5 0.629938 |
| 14 8.958e-02 1.144e+00 5 0.601600 |
| 15 1.613e-01 1.488e+00 5 0.554602 |
| 16 1.832e-01 1.961e+00 5 0.532888 |
| 17 1.883e-01 1.876e+00 5 0.532621 |
| 18 1.609e-01 2.334e+00 4 0.520117 |
| 19 1.114e-01 3.481e+00 5 0.434571 |
| 20 7.493e-02 4.892e+00 5 0.449733 |
| 21 1.290e-01 2.424e+00 5 0.438712 |
| 22 1.147e-01 7.662e+00 5 0.402852 |
| 23 7.109e-02 1.921e+00 5 0.392863 |
| 24 5.848e-02 1.709e+00 5 0.380071 |
| 25 1.549e-01 1.580e+00 4 0.381998 |
| 26 1.625e-01 2.766e+00 4 0.382241 |
| 27 6.413e-02 2.175e+00 4 0.393642 |
| 28 5.137e-02 1.453e+00 4 0.365978 |
| 29 1.266e-01 2.768e+00 4 0.352593 |
| 30 4.086e-02 9.296e-01 4 0.348628 |
| 31 1.287e-01 1.989e+00 4 0.339829 |
| 32 4.591e-02 1.452e+00 4 0.340066 |
| 33 7.947e-02 9.345e-01 4 0.341770 |
| 34 1.462e-01 1.747e+00 4 0.353379 |
| 35 1.292e-01 3.906e+00 4 0.381371 |
| 36 6.650e-02 2.056e+00 4 0.378206 |
| 37 8.992e-02 7.477e-01 4 0.372127 |
| 38 5.721e-02 4.661e-01 4 0.361421 |
| 39 7.983e-02 7.730e-01 4 0.342288 |
| 40 4.963e-02 8.188e-01 4 0.324326 |
| 41 4.704e-02 8.541e-01 4 0.306461 |
| 42 8.092e-02 8.304e-01 4 0.292080 |
| 43 9.223e-02 9.421e-01 4 0.287996 |
| 44 3.542e-02 6.786e-01 4 0.286875 |
| 45 6.534e-02 6.013e-01 4 0.281882 |
| 46 7.977e-02 7.766e-01 4 0.291941 |
| 47 8.681e-02 5.456e-01 4 0.289363 |
| 48 5.494e-02 5.299e-01 3 0.288635 |
| 49 3.637e-02 5.101e-01 3 0.273450 |
| 50 3.460e-02 5.031e-01 4 0.267689 |
| 51 6.985e-02 9.933e-01 4 0.265413 |
| 52 2.029e-02 5.936e-01 4 0.264947 |
| 53 3.018e-02 3.944e-01 4 0.262447 |
| 54 3.141e-02 2.750e-01 4 0.258681 |
| 55 4.305e-02 2.439e-01 4 0.256390 |
| 56 7.651e-02 3.663e-01 4 0.257563 |
| 57 2.460e-02 2.903e-01 4 0.251078 |
| 58 7.070e-02 2.161e-01 4 0.251786 |
| 59 3.378e-02 3.596e-01 4 0.252871 |
| 60 1.819e-02 2.611e-01 4 0.251387 |
| 61 1.766e-02 1.481e-01 4 0.251193 |
| 62 1.322e-02 1.567e-01 4 0.250207 |
| 63 2.475e-02 1.361e-01 4 0.249766 |
| 64 3.006e-02 2.371e-01 4 0.250092 |
| 65 7.935e-03 1.005e-01 4 0.248043 |
| 66 7.304e-03 9.936e-02 4 0.246630 |
| 67 2.141e-02 1.508e-01 4 0.244856 |
| 68 4.312e-02 4.002e-01 4 0.242708 |
| 69 5.923e-02 6.326e-01 4 0.241984 |
| 70 6.366e-02 6.439e-01 4 0.241400 |
| 71 5.622e-02 8.051e-01 4 0.238383 |
| 72 1.006e-01 6.955e-01 5 0.256355 |
| 73 3.685e-02 4.516e-01 4 0.237830 |
| 74 4.681e-02 3.641e-01 4 0.232630 |
| 75 4.393e-02 5.761e-01 4 0.224798 |
| 76 7.176e-02 1.222e+00 5 0.260728 |
| 77 5.037e-02 7.388e-01 5 0.225165 |
| 78 4.955e-02 3.884e-01 4 0.218996 |
| 79 1.978e-02 3.305e-01 4 0.212795 |
| 80 3.705e-02 3.893e-01 4 0.204375 |
| 81 1.532e-02 4.015e-01 4 0.201892 |
| 82 1.262e-02 3.243e-01 4 0.197980 |
| 83 1.170e-02 2.455e-01 4 0.194299 |
| 84 6.470e-02 5.046e-01 5 0.182382 |
| 85 4.025e-02 6.853e-01 5 0.163395 |
| 86 2.841e-02 7.090e-01 4 0.151578 |
Title: Re: Estimate the convergence of NEB
Post by: Jess Wellendorff on February 29, 2016, 08:41: There is no reason to believe that the NEB in question will not converge. The maximum energy (right-most column) is going down steadily, especially in the last few iterations of that output.
Title: Re: Estimate the convergence of NEB
Post by: baizq on February 29, 2016, 18:38: Thank you, Jess. Does that mean if we observe steady decrease of maximum energy, though the maximum force and the step length fluctuate, we should be positive and look forward to a convergence?
Title: Re: Estimate the convergence of NEB
Post by: baizq on February 29, 2016, 19:35: A further question: is there a way to resume an NEB calculation from nc file?
Title: Re: Estimate the convergence of NEB
Post by: baizq on February 29, 2016, 20:03: The calculation is ongoing, giving out further odd results as follows. The number of max. energy image goes to zero, so does the max. energy. May I know whether this is a bug?

| 87 2.090e-02 3.245e-01 4 0.133771 |
| 88 1.935e-02 3.313e-01 4 0.118799 |
| 89 4.415e-02 4.111e-01 4 0.092446 |
| 90 7.824e-02 1.277e+00 3 0.050403 |
| 91 3.060e-02 1.084e+00 3 0.050471 |
| 92 5.522e-02 4.922e-01 4 0.057512 |
| 93 4.411e-02 4.008e-01 4 0.047241 |
| 94 8.345e-02 5.668e-01 0 0.000000 |
| 95 1.268e-01 9.273e-01 0 0.000000 |
| 96 5.342e-02 2.655e+00 0 0.000000 |
| 97 1.153e-01 2.513e+00 0 0.000000 |
| 98 9.663e-02 3.551e+00 0 0.000000 |
Title: Re: Estimate the convergence of NEB
Post by: Jess Wellendorff on March 1, 2016, 13:11: Perhaps I could have a look at your script? You can send it privately if you like: jess.wellendorff@quantumwise.com
Title: Re: Estimate the convergence of NEB
Post by: baizq on March 2, 2016, 20:15: Thank you, Jess. Sure, I have sent you the script.