relaxing a system before testing

Dear users,

I am relaxing a CNT bundle. I hold its ends fixed and apply fix nve and fix temp/rescale to thermostat the non-end atoms to 0.5 K.

But how do I know when my system is relaxed or stable and ready to do mechanical testing on?

See the data below. For example did I really need 20,000 timesteps since the temp seems to be held constant at approx. 0.5 K very quickly?

Thanks for your help

Daniel

LOG FILE DATA DURING RELAXATION:

Step Temp PotEng KinEng TotEng Pzz Zlo Zhi

0 0.49026553 -132951.57 1.1718078 -132950.4 -0.29054226 -1000 1000

100 0.49026553 -132953.35 1.1718078 -132952.18 -0.29672979 -1000 1000

200 0.49026553 -132954.24 1.1718078 -132953.07 -0.29585836 -1000 1000

300 0.4908478 -132954.61 1.1731996 -132953.44 -0.29522833 -1000 1000

400 0.4921707 -132954.89 1.1763615 -132953.71 -0.29802676 -1000 1000

500 0.49161303 -132955.01 1.1750286 -132953.83 -0.29813068 -1000 1000

600 0.48964834 -132955.05 1.1703327 -132953.88 -0.29654123 -1000 1000

700 0.48946677 -132955.01 1.1698987 -132953.84 -0.29727645 -1000 1000

800 0.48993732 -132954.9 1.1710234 -132953.73 -0.29659224 -1000 1000

900 0.48901315 -132954.88 1.1688145 -132953.71 -0.29766415 -1000 1000

1000 0.48887363 -132954.85 1.168481 -132953.68 -0.2971225 -1000 1000

1100 0.49026553 -132954.76 1.1718078 -132953.59 -0.29672256 -1000 1000

1200 0.48853866 -132954.63 1.1676803 -132953.46 -0.2980849 -1000 1000

1300 0.49079761 -132954.58 1.1730796 -132953.4 -0.29778274 -1000 1000

1400 0.49095059 -132954.58 1.1734452 -132953.41 -0.29646539 -1000 1000

1500 0.49198297 -132954.58 1.1759128 -132953.4 -0.29792705 -1000 1000

1600 0.48862702 -132954.54 1.1678915 -132953.37 -0.29819979 -1000 1000

1700 0.4908417 -132954.59 1.173185 -132953.41 -0.29784867 -1000 1000

1800 0.49026553 -132954.68 1.1718078 -132953.51 -0.2980868 -1000 1000

1900 0.49060973 -132954.75 1.1726305 -132953.57 -0.29745599 -1000 1000

2000 0.49099592 -132954.77 1.1735536 -132953.6 -0.29866075 -1000 1000

2100 0.49042615 -132954.81 1.1721917 -132953.64 -0.29875402 -1000 1000

2200 0.49026553 -132954.9 1.1718078 -132953.73 -0.29770929 -1000 1000

2300 0.49220683 -132954.98 1.1764478 -132953.81 -0.29920776 -1000 1000

2400 0.49069104 -132955.04 1.1728249 -132953.87 -0.29879893 -1000 1000

2500 0.49132853 -132955.03 1.1743486 -132953.86 -0.29789838 -1000 1000

2600 0.4911544 -132955.06 1.1739324 -132953.88 -0.29740391 -1000 1000

2700 0.48987302 -132955.02 1.1708697 -132953.85 -0.29684263 -1000 1000

2800 0.4897358 -132954.92 1.1705417 -132953.75 -0.29717338 -1000 1000

2900 0.48937103 -132954.81 1.1696699 -132953.64 -0.29843536 -1000 1000

3000 0.49017031 -132954.79 1.1715803 -132953.62 -0.29803855 -1000 1000

3100 0.49114353 -132954.87 1.1739064 -132953.69 -0.29908448 -1000 1000

3200 0.49002841 -132954.91 1.1712411 -132953.74 -0.29846035 -1000 1000

3300 0.49149569 -132954.91 1.1747481 -132953.74 -0.29805917 -1000 1000

3400 0.49122036 -132954.93 1.17409 -132953.76 -0.2984763 -1000 1000

3500 0.49045903 -132954.95 1.1722703 -132953.77 -0.2987407 -1000 1000

3600 0.49176269 -132954.97 1.1753863 -132953.79 -0.29878482 -1000 1000

3700 0.48977285 -132954.94 1.1706303 -132953.77 -0.29858158 -1000 1000

3800 0.48954165 -132954.9 1.1700776 -132953.73 -0.29832592 -1000 1000

3900 0.48926683 -132954.9 1.1694208 -132953.73 -0.29754473 -1000 1000

4000 0.4921364 -132954.88 1.1762795 -132953.71 -0.29907475 -1000 1000

4100 0.48868422 -132954.88 1.1680283 -132953.71 -0.29948894 -1000 1000

4200 0.48875043 -132954.84 1.1681865 -132953.67 -0.29941939 -1000 1000

4300 0.49140165 -132954.89 1.1745233 -132953.71 -0.29908491 -1000 1000

4400 0.48919714 -132954.91 1.1692542 -132953.74 -0.29738122 -1000 1000

4500 0.49026923 -132954.91 1.1718167 -132953.74 -0.29710528 -1000 1000

4600 0.49190435 -132954.93 1.1757249 -132953.76 -0.29803811 -1000 1000

4700 0.49026553 -132954.99 1.1718078 -132953.82 -0.29672858 -1000 1000

4800 0.49099945 -132955.03 1.173562 -132953.86 -0.29640481 -1000 1000

4900 0.49016763 -132955.03 1.1715738 -132953.86 -0.29730987 -1000 1000

5000 0.49089462 -132955.03 1.1733115 -132953.85 -0.29766255 -1000 1000

5100 0.4901768 -132955.05 1.1715958 -132953.88 -0.2982567 -1000 1000

5200 0.4883929 -132955.07 1.167332 -132953.91 -0.29793732 -1000 1000

5300 0.49026553 -132955.03 1.1718078 -132953.86 -0.2979452 -1000 1000

5400 0.48993651 -132955 1.1710214 -132953.83 -0.29720927 -1000 1000

5500 0.49183462 -132955.01 1.1755582 -132953.83 -0.29689954 -1000 1000

5600 0.48889055 -132955.02 1.1685214 -132953.85 -0.29683409 -1000 1000

5700 0.48886259 -132954.99 1.1684546 -132953.82 -0.29769977 -1000 1000

5800 0.49032029 -132954.98 1.1719387 -132953.81 -0.29744484 -1000 1000

5900 0.49023425 -132954.97 1.1717331 -132953.8 -0.2970182 -1000 1000

6000 0.49111985 -132954.97 1.1738498 -132953.8 -0.29745336 -1000 1000

6100 0.4894838 -132954.98 1.1699394 -132953.81 -0.29843673 -1000 1000

6200 0.4898515 -132954.97 1.1708183 -132953.8 -0.29801729 -1000 1000

6300 0.49041159 -132954.97 1.1721569 -132953.8 -0.29793315 -1000 1000

6400 0.49168343 -132955.02 1.1751968 -132953.84 -0.29818386 -1000 1000

6500 0.48954898 -132955.04 1.1700952 -132953.87 -0.29786835 -1000 1000

6600 0.49212697 -132955.02 1.1762569 -132953.84 -0.29735687 -1000 1000

6700 0.49026553 -132955.04 1.1718078 -132953.87 -0.29729848 -1000 1000

6800 0.48882905 -132955.05 1.1683744 -132953.88 -0.29743765 -1000 1000

6900 0.48995905 -132955.04 1.1710753 -132953.87 -0.29742318 -1000 1000

7000 0.49129355 -132955.06 1.174265 -132953.89 -0.29709979 -1000 1000

7100 0.49067345 -132955.11 1.1727828 -132953.94 -0.29731655 -1000 1000

7200 0.48958471 -132955.14 1.1701806 -132953.97 -0.29706231 -1000 1000

7300 0.48873908 -132955.12 1.1681594 -132953.95 -0.29804623 -1000 1000

7400 0.489857 -132955.07 1.1708314 -132953.9 -0.29719959 -1000 1000

7500 0.491483 -132955.07 1.1747178 -132953.9 -0.29702638 -1000 1000

7600 0.48968589 -132955.06 1.1704224 -132953.89 -0.29822825 -1000 1000

7700 0.49026553 -132955.03 1.1718078 -132953.86 -0.29756836 -1000 1000

7800 0.48999689 -132955.02 1.1711658 -132953.85 -0.29700712 -1000 1000

7900 0.49059547 -132955.01 1.1725964 -132953.84 -0.29665301 -1000 1000

8000 0.49046527 -132955.04 1.1722852 -132953.87 -0.29699886 -1000 1000

8100 0.49048373 -132955.04 1.1723294 -132953.86 -0.2972834 -1000 1000

8200 0.49091415 -132955.06 1.1733581 -132953.89 -0.29694559 -1000 1000

8300 0.49054332 -132955.07 1.1724718 -132953.89 -0.29648892 -1000 1000

8400 0.49066278 -132955.07 1.1727573 -132953.9 -0.29752456 -1000 1000

8500 0.48999838 -132955.07 1.1711693 -132953.9 -0.29740772 -1000 1000

8600 0.48872995 -132955.07 1.1681376 -132953.9 -0.29707621 -1000 1000

8700 0.48880625 -132955.03 1.1683199 -132953.86 -0.29561595 -1000 1000

8800 0.48919348 -132954.99 1.1692455 -132953.82 -0.29557196 -1000 1000

8900 0.48890364 -132954.95 1.1685527 -132953.78 -0.296888 -1000 1000

9000 0.48933879 -132954.89 1.1695928 -132953.72 -0.29667251 -1000 1000

9100 0.48933779 -132954.91 1.1695904 -132953.74 -0.29549157 -1000 1000

9200 0.49086251 -132954.89 1.1732347 -132953.72 -0.29584829 -1000 1000

9300 0.48879757 -132954.88 1.1682992 -132953.71 -0.2958714 -1000 1000

9400 0.49177647 -132954.91 1.1754192 -132953.74 -0.29593674 -1000 1000

9500 0.48999462 -132954.94 1.1711603 -132953.77 -0.295876 -1000 1000

9600 0.48955511 -132954.97 1.1701098 -132953.8 -0.29717017 -1000 1000

9700 0.48899733 -132954.96 1.1687766 -132953.8 -0.29718972 -1000 1000

9800 0.48879838 -132954.95 1.1683011 -132953.78 -0.29664994 -1000 1000

9900 0.49085618 -132954.97 1.1732196 -132953.8 -0.29691078 -1000 1000

10000 0.49053456 -132955.01 1.1724509 -132953.84 -0.29621497 -1000 1000

10100 0.49099381 -132955.03 1.1735485 -132953.86 -0.29586463 -1000 1000

10200 0.49063696 -132955.05 1.1726956 -132953.88 -0.29663526 -1000 1000

10300 0.49094208 -132955.05 1.1734249 -132953.88 -0.29581807 -1000 1000

10400 0.49046849 -132955.07 1.1722929 -132953.9 -0.29629614 -1000 1000

10500 0.48831666 -132955.05 1.1671497 -132953.88 -0.29755157 -1000 1000

10600 0.49034691 -132955 1.1720024 -132953.82 -0.2972987 -1000 1000

10700 0.49063438 -132955.01 1.1726894 -132953.84 -0.29620555 -1000 1000

10800 0.48899082 -132955 1.1687611 -132953.83 -0.29691667 -1000 1000

10900 0.49022269 -132954.99 1.1717054 -132953.82 -0.29690508 -1000 1000

11000 0.48934237 -132954.99 1.1696013 -132953.82 -0.29806475 -1000 1000

11100 0.49221445 -132955 1.176466 -132953.82 -0.29742988 -1000 1000

11200 0.48935053 -132955.01 1.1696208 -132953.84 -0.29568731 -1000 1000

11300 0.48897167 -132954.99 1.1687153 -132953.82 -0.29594886 -1000 1000

11400 0.49180146 -132954.98 1.1754789 -132953.81 -0.29650756 -1000 1000

11500 0.49189779 -132954.99 1.1757092 -132953.81 -0.29649201 -1000 1000

11600 0.48935826 -132954.99 1.1696393 -132953.82 -0.29786722 -1000 1000

11700 0.49031187 -132954.99 1.1719186 -132953.81 -0.29771977 -1000 1000

11800 0.4889078 -132954.96 1.1685626 -132953.79 -0.2974982 -1000 1000

11900 0.49008714 -132954.94 1.1713815 -132953.76 -0.29851436 -1000 1000

12000 0.48868819 -132954.91 1.1680377 -132953.75 -0.29653545 -1000 1000

12100 0.4901108 -132954.9 1.171438 -132953.73 -0.29688222 -1000 1000

12200 0.48969473 -132954.89 1.1704435 -132953.72 -0.29818829 -1000 1000

12300 0.49206937 -132954.9 1.1761193 -132953.73 -0.29631529 -1000 1000

12400 0.49085782 -132954.92 1.1732235 -132953.75 -0.29733684 -1000 1000

12500 0.49105106 -132954.95 1.1736854 -132953.78 -0.29929498 -1000 1000

12600 0.49135506 -132954.99 1.174412 -132953.81 -0.2977142 -1000 1000

12700 0.49115699 -132955 1.1739386 -132953.83 -0.29818275 -1000 1000

12800 0.49126641 -132955.03 1.1742001 -132953.86 -0.29838352 -1000 1000

12900 0.48949612 -132955.02 1.1699688 -132953.85 -0.29601342 -1000 1000

13000 0.48990207 -132955 1.1709391 -132953.83 -0.2978662 -1000 1000

13100 0.49033975 -132955 1.1719852 -132953.83 -0.29763909 -1000 1000

13200 0.48893893 -132954.99 1.1686371 -132953.82 -0.29555446 -1000 1000

13300 0.48877583 -132954.97 1.1682472 -132953.8 -0.29777826 -1000 1000

13400 0.48972604 -132954.94 1.1705184 -132953.77 -0.29781498 -1000 1000

13500 0.49084278 -132954.94 1.1731876 -132953.77 -0.29682574 -1000 1000

13600 0.49112673 -132954.98 1.1738662 -132953.8 -0.29785583 -1000 1000

13700 0.48941621 -132954.98 1.1697778 -132953.81 -0.2972354 -1000 1000

13800 0.49135047 -132954.97 1.174401 -132953.8 -0.2981229 -1000 1000

13900 0.48980825 -132954.98 1.1707149 -132953.81 -0.29855705 -1000 1000

14000 0.49134814 -132955 1.1743954 -132953.83 -0.29617208 -1000 1000

14100 0.49085469 -132955.02 1.173216 -132953.85 -0.29577527 -1000 1000

14200 0.49026553 -132955.03 1.1718078 -132953.86 -0.2959305 -1000 1000

14300 0.49098143 -132955.05 1.173519 -132953.88 -0.29489171 -1000 1000

14400 0.4905621 -132955.05 1.1725167 -132953.88 -0.29578228 -1000 1000

14500 0.48901758 -132955.06 1.1688251 -132953.89 -0.29686566 -1000 1000

14600 0.49026553 -132955.04 1.1718078 -132953.87 -0.29655136 -1000 1000

14700 0.49133017 -132955.04 1.1743525 -132953.86 -0.29761392 -1000 1000

14800 0.48961204 -132955.05 1.1702459 -132953.88 -0.29618721 -1000 1000

14900 0.49026553 -132955.05 1.1718078 -132953.88 -0.29580986 -1000 1000

15000 0.49086121 -132955.07 1.1732316 -132953.9 -0.2966315 -1000 1000

15100 0.49161926 -132955.08 1.1750434 -132953.9 -0.29697876 -1000 1000

15200 0.49159884 -132955.1 1.1749946 -132953.93 -0.29571459 -1000 1000

15300 0.48852575 -132955.11 1.1676495 -132953.94 -0.29708394 -1000 1000

15400 0.49153571 -132955.12 1.1748438 -132953.94 -0.2963265 -1000 1000

15500 0.49076567 -132955.14 1.1730032 -132953.97 -0.295572 -1000 1000

15600 0.49177017 -132955.16 1.1754041 -132953.99 -0.29570418 -1000 1000

15700 0.49176919 -132955.19 1.1754018 -132954.02 -0.2951835 -1000 1000

15800 0.48923811 -132955.17 1.1693521 -132954 -0.29579532 -1000 1000

15900 0.49064617 -132955.17 1.1727176 -132954 -0.2952297 -1000 1000

16000 0.48861737 -132955.17 1.1678685 -132954 -0.2946899 -1000 1000

16100 0.48906415 -132955.14 1.1689363 -132953.97 -0.29587521 -1000 1000

16200 0.49035107 -132955.11 1.1720123 -132953.93 -0.2957206 -1000 1000

16300 0.49097895 -132955.13 1.173513 -132953.95 -0.29493528 -1000 1000

16400 0.49070633 -132955.13 1.1728614 -132953.95 -0.2950116 -1000 1000

16500 0.48865662 -132955.12 1.1679623 -132953.95 -0.29390762 -1000 1000

16600 0.48978711 -132955.09 1.1706643 -132953.92 -0.29392219 -1000 1000

16700 0.49087309 -132955.09 1.17326 -132953.92 -0.294974 -1000 1000

16800 0.49094069 -132955.09 1.1734216 -132953.92 -0.29442466 -1000 1000

16900 0.49186952 -132955.11 1.1756416 -132953.94 -0.29397496 -1000 1000

17000 0.48950308 -132955.12 1.1699855 -132953.95 -0.29484037 -1000 1000

17100 0.4892785 -132955.1 1.1694487 -132953.93 -0.29401459 -1000 1000

17200 0.49055862 -132955.11 1.1725084 -132953.94 -0.29486597 -1000 1000

17300 0.4889905 -132955.1 1.1687603 -132953.93 -0.2949946 -1000 1000

17400 0.48873739 -132955.09 1.1681553 -132953.92 -0.29478496 -1000 1000

17500 0.48968596 -132955.08 1.1704226 -132953.91 -0.29516062 -1000 1000

17600 0.49194029 -132955.07 1.1758108 -132953.89 -0.29548273 -1000 1000

17700 0.49192048 -132955.11 1.1757634 -132953.94 -0.29485089 -1000 1000

17800 0.48926182 -132955.1 1.1694088 -132953.94 -0.29426227 -1000 1000

17900 0.4899393 -132955.07 1.1710281 -132953.9 -0.29471232 -1000 1000

18000 0.49074652 -132955.07 1.1729575 -132953.9 -0.29453738 -1000 1000

18100 0.49007906 -132955.08 1.1713621 -132953.91 -0.29514622 -1000 1000

18200 0.49189743 -132955.08 1.1757083 -132953.9 -0.29498993 -1000 1000

18300 0.48900911 -132955.06 1.1688048 -132953.9 -0.29511435 -1000 1000

18400 0.4920199 -132955.07 1.1760011 -132953.9 -0.2948459 -1000 1000

18500 0.48992721 -132955.07 1.1709992 -132953.9 -0.29368575 -1000 1000

18600 0.48954759 -132955.07 1.1700919 -132953.9 -0.29393943 -1000 1000

18700 0.49136147 -132955.08 1.1744273 -132953.91 -0.293894 -1000 1000

18800 0.49061111 -132955.11 1.1726338 -132953.93 -0.29398101 -1000 1000

18900 0.48913568 -132955.12 1.1691073 -132953.95 -0.29498538 -1000 1000

19000 0.48964944 -132955.11 1.1703353 -132953.93 -0.29477744 -1000 1000

19100 0.48946671 -132955.08 1.1698985 -132953.91 -0.29416067 -1000 1000

19200 0.49035221 -132955.07 1.172015 -132953.89 -0.29356106 -1000 1000

19300 0.4889385 -132955.06 1.168636 -132953.89 -0.29240122 -1000 1000

19400 0.48840518 -132955.04 1.1673613 -132953.87 -0.29233712 -1000 1000

19500 0.49052653 -132955.04 1.1724317 -132953.87 -0.29329449 -1000 1000

19600 0.49037853 -132955.05 1.1720779 -132953.87 -0.29305674 -1000 1000

19700 0.48987778 -132955.03 1.170881 -132953.86 -0.29325595 -1000 1000

19800 0.49045504 -132955.02 1.1722608 -132953.85 -0.29458061 -1000 1000

19900 0.49112985 -132955.03 1.1738737 -132953.86 -0.29417309 -1000 1000

20000 0.49102829 -132955.04 1.1736309 -132953.87 -0.29360777 -1000 1000

……………………………………………………………………………………………………………

Daniel Mulvihill B.Eng., D.Phil. (Oxon). MIMechE MIEI

Government of Ireland Research Fellow,

Department of Mechanical, Aeronautical, and Biomedical Enginering,

University of Limerick

Dear users,

I am relaxing a CNT bundle. I hold its ends fixed and apply fix nve and fix
temp/rescale to thermostat the non-end atoms to 0.5 K.

But how do I know when my system is relaxed or stable and ready to do
mechanical testing on?

with temp/rescale, you will *never* have a really relaxed system,
since every time rescaling happens, it is as if you are giving all the
atoms a kick. other than that, there is plenty of text book literature
around explaining how to estimate the progress of
equilibration/relaxation. no point to repeat this here.

furthermore, if you run at 0.5K. what kind of barrier would you expect
to cross the system into a lower energy state? your system will just
stay in whatever (local?) minimum you are in unless you have an
extremely shallow potential energy hypersurface.

whatever you do, you always need to make an educated guess or better
and choose for yourself. what may be a good choice for one purpose,
can be very bad for another.

See the data below. For example did I really need 20,000 timesteps since
the temp seems to be held constant at approx. 0.5 K very quickly?

as explained many, many times. incomplete data (e.g. output without
matching input or incomplete inputs) does not allow for many qualified
comments.

axel.

Thank you very much Axel

I will look at the text books on this. But is it the case that when an
approximately constant temp, pot energy and kinetic energy are reached
we have a relaxed and stable system?
So I only need as many steps as are needed to have constant temp and
energy output in the log file?
I know this is not really a lammps question.

Also I think you prefer fix nvt instead of fix nve with velocity temp
rescale for thermostating (if im correct) -why is this and is fix nvt
as versatile?

Daniel