Residual Stresses in a Polymer System

Hello all,

I have been trying to equilibrate a polymer system and perform minimizations to zero out residual stresses in it. I am using reaxff potential. I am seeing that during equilibration as well as minimization, v_press (residual stress) value is fluctuating too much, instead of decreasing. Does this mean I should take more atoms? At this point, I am taking nearly 4000 atoms

Following is input script and few runs:

Step Temp PotEng TotEng Press Pxx Pyy Pzz Density Fmax v_press
0 0 -420737.04 -420737.04 24356.803 30366.154 20288.133 22416.121 1.2046391 656.47663 24356.803
100 191.47409 -422979.73 -420738.4 41324.509 42040.225 39006.141 42927.161 1.2046391 592.02869 41324.509
200 246.02642 -423622.04 -420742.14 25607.928 26967.009 22018.117 27838.656 1.2046391 543.8521 25607.928
300 269.25946 -423899.53 -420747.68 38003.624 38247.951 39019.723 36743.198 1.2046391 545.26153 38003.624
400 274.66206 -423970.82 -420755.73 26364.738 23612.266 27068.79 28413.157 1.2046391 608.66833 26364.738
500 283.1951 -424077.09 -420762.11 30132.244 28503.629 28633.48 33259.622 1.2046391 437.02302 30132.244
600 285.07383 -424110.24 -420773.26 28100.429 27497.534 30005.697 26798.055 1.2046391 465.96733 28100.429
700 281.77653 -424077.26 -420778.88 28652.645 29828.873 25756.474 30372.588 1.2046391 578.93835 28652.645
800 285.75415 -424121.2 -420776.27 28958.19 27892.42 29026.081 29956.068 1.2046391 720.8539 28958.19
900 290.55835 -424175.93 -420774.76 35020.451 31767.936 39136.743 34156.675 1.2046391 587.23506 35020.451
1000 289.69051 -424164.88 -420773.87 36360.592 34154.167 36397.649 38529.962 1.2046391 812.6257 36360.592
1100 290.24212 -424179.86 -420782.39 29541.412 30635.133 27824.161 30164.941 1.2046391 560.94547 29541.412
1200 288.14008 -424161.06 -420788.2 30259.371 31567.956 28960.119 30250.039 1.2046391 345.73492 30259.371
1300 290.22383 -424185.66 -420788.41 34098.076 31988.555 33770.287 36535.385 1.2046391 530.21613 34098.076
1400 291.08699 -424182.08 -420774.72 29182.317 28244.647 28490.733 30811.571 1.2046391 357.04545 29182.317
1500 290.79549 -424163.41 -420759.46 31514.916 28196.388 30732.941 35615.418 1.2046391 408.38587 31514.916
1600 289.70942 -424156.12 -420764.89 30737.356 27626.401 32736.144 31849.522 1.2046391 533.61793 30737.356
1700 291.92871 -424176.62 -420759.4 31738.975 30747.971 33475.943 30993.012 1.2046391 801.20377 31738.975
1800 289.18573 -424148.44 -420763.33 28249.868 28024.459 28551.034 28174.113 1.2046391 551.74582 28249.868
1900 285.5297 -424102.73 -420760.42 31184.026 31609.39 32239.673 29703.014 1.2046391 600.40771 31184.026
2000 290.1917 -424169.38 -420772.5 26386.233 25576.436 30712.353 22869.909 1.2046391 456.92627 26386.233
2100 287.50247 -424129.67 -420764.26 29192.378 27666.932 33004.61 26905.591 1.2046391 430.6528 29192.378
2200 289.12704 -424150.84 -420766.43 30721.006 28708.708 32267.713 31186.597 1.2046391 427.28256 30721.006
2300 291.47775 -424175.79 -420763.86 35184.225 34637.661 40092.548 30822.467 1.2046391 485.89241 35184.225
2400 292.92949 -424186.12 -420757.2 27577.643 24099.971 33084.651 25548.308 1.2046391 805.05033 27577.643
2500 298.50731 -424254.08 -420759.86 29889.737 29125.501 32194.406 28349.305 1.2046391 386.72931 29889.737
2600 297.12925 -424235.53 -420757.45 34561.087 37173.683 30542.786 35966.791 1.2046391 431.09072 34561.087
2700 296.51006 -424222.38 -420751.54 31439.53 28510.273 34652.341 31155.977 1.2046391 665.16621 31439.53
2800 295.76428 -424215.23 -420753.12 24572.199 23855.864 27243.713 22617.02 1.2046391 412.87624 24572.199
2900 296.80984 -424235.13 -420760.78 30470.6 28326.695 33632.811 29452.293 1.2046391 501.88868 30470.6
3000 295.5854 -424215.91 -420755.89 29552.063 28307.624 31711.052 28637.514 1.2046391 516.81283 29552.063
3100 295.08913 -424217.15 -420762.94 26969.759 24852.893 26613.308 29443.075 1.2046391 782.41314 26969.759
3200 294.40903 -424202.58 -420756.33 27543.742 25969.279 27873.256 28788.69 1.2046391 534.56565 27543.742
3300 296.08302 -424224.9 -420759.06 33696.81 33823.02 31450.744 35816.665 1.2046391 486.98742 33696.81
3400 297.48316 -424252.1 -420769.86 33756.07 31515.615 37853.754 31898.841 1.2046391 692.2978 33756.07
3500 296.50852 -424231.78 -420760.96 25371.611 27086.082 23033.564 25995.186 1.2046391 500.02693 25371.611
3600 293.67034 -424203.09 -420765.5 35956.268 35688.373 34741.549 37438.881 1.2046391 508.84834 35956.268
3700 299.46843 -424273.09 -420767.62 27200.515 29615.741 29736.87 22248.934 1.2046391 326.74109 27200.515
3800 301.57895 -424311.08 -420780.9 28685.655 29761.661 30447.09 25848.213 1.2046391 482.18604 28685.655
3900 304.6155 -424342.2 -420776.48 32186.486 33189.062 34727.756 28642.64 1.2046391 396.95017 32186.486
4000 298.67184 -424279.16 -420783.01 28728.136 29402.306 27558.705 29223.398 1.2046391 671.27124 28728.136
4100 302.12654 -424304.77 -420768.19 33253.569 33673.465 35337.586 30749.654 1.2046391 451.05811 33253.569
4200 300.817 -424282.95 -420761.7 33458.986 30539.687 38456.174 31381.097 1.2046391 396.36699 33458.986
4300 302.59388 -424305.74 -420763.69 30607.853 29831.547 30330.2 31661.813 1.2046391 574.49324 30607.853
4400 301.01659 -424285.2 -420761.61 29735.33 29582.901 29961.956 29661.133 1.2046391 450.91476 29735.33
4500 305.89865 -424345.92 -420765.18 30298.286 33598.264 30408.011 26888.584 1.2046391 609.15388 30298.286
4600 303.14751 -424321.01 -420772.47 31622.765 27436.849 32688.074 34743.372 1.2046391 374.23909 31622.765
4700 305.06921 -424349.68 -420778.65 32823.322 32517.112 31892.269 34060.585 1.2046391 359.37081 32823.322
4800 305.11554 -424347.1 -420775.53 33691.274 31526.015 30971.053 38576.752 1.2046391 606.81012 33691.274
4900 304.41412 -424323.96 -420760.59 33508.206 37158.721 30498.28 32867.617 1.2046391 475.18991 33508.206
5000 305.96309 -424334.72 -420753.22 27729.316 28795.002 24941.858 29451.089 1.2046391 441.79234 27729.316
Loop time of 4329.29 on 1 procs for 5000 steps with 3928 atoms

Performance: 0.010 ns/day, 2405.158 hours/ns, 1.155 timesteps/s
99.2% CPU use with 1 MPI tasks x 1 OpenMP threads

MPI task timing breakdown:
Section | min time | avg time | max time |%varavg| %total