<div dir="ltr"><div>Hello Wanlu,</div><div> </div><div>I think this a normal behaviour. Temperature is thermostatistical property, then its significance is "real" when you use an average over time or particles. When you run a MD with hundreds of particles, you have a particle average at each frame, but when you use a single particle, the temperature is not well defined for each frame, but the time average temperature its better defined. As an example, a single particle harmonic oscillator, you define an initial and conserved total energy, the particle changes their potential and kinetic energy along the parabola, at the left and the right "all" (forgot the zero point energy) the energy is potential energy, and in the middle "all" is kinetic, the kinetic energy (and the particle temperature) oscillate from total energy (the highest temperature) to zero in an harmonic framework, and the time average gives you the thermostatistic temperature. If you couple a thermostat to regulate the temperature, you will add and subtract kinetic energy depending the time local situation, and never achieve the equilibrium.</div><div>This is what happens in a single molecule MD (with some differences from the previous picture, due to the oscillators are not totally harmonic, and the time integration is not infinitesimal).</div><div>If you want to simulate a single molecule at a particular temperature T*, I recommend to run a NVE MD, with an initial temperature of 2T*, and a minimum energy geometry (at the same level of theory). In this framework, from the equipartition principle, half of kinetic energy goes to the potential energy (the average values) and the average temperature would T*, or very near (due to the system and the simulation are not ideal or perfect). This is like as running a harmonic MD with an initial geometry in the bottom of the parabola, and giving some kinetic energy (where kinetic energy is equal to total energy at the beginning).</div><div> </div><div>Regards! </div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">El sáb., 28 mar. 2020 a las 20:48, Wan-Lu Li (<<a href="mailto:wanlu...@gmail.com">wanlu...@gmail.com</a>>) escribió: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Dear CP2K users,<div> </div><div>Now I'm running the AIMD simulation for CO molecule at 300K under NVT ensemble to calculate the time averaged energy. But I found the temperature fluctuation is very large (even for 2ps), while the energy seems quite converged. I attached part of my CO.ener file here and the end is my input file. Is this case normal and can I use the averaged energy from the fifth column? Thanks a lot for your help in advance.</div><div> </div><div>Best regards,</div><div>Wanlu</div><div> </div><div>part of the CO.ener file:</div><div># Step Nr. Time[fs] Kin.[a.u.] Temp[K] Pot.[a.u.] Cons Qty[a.u.] UsedTime[s] 0 0.000000 0.001425067 300.000000000 -21.617781192 -21.616356125 0.000000000 1 1.000000 0.000692729 145.830941811 -21.617837920 -21.616358277 194.412350386 2 2.000000 0.000839725 176.775929504 -21.617886447 -21.616360106 46.210681908 3 3.000000 0.001256199 264.450456994 -21.617967921 -21.616363102 57.633208051 4 4.000000 0.000374173 78.769638799 -21.617973412 -21.616363182 46.150063051 5 5.000000 0.000559107 117.701236643 -21.617953442 -21.616361844 59.398619272 6 6.000000 0.002482481 522.602979873 -21.617783307 -21.616353176 106.069239420 7 7.000000 0.001196440 251.870238012 -21.617652842 -21.616346215 58.390943444 8 8.000000 0.001901098 400.212437908 -21.617651021 -21.616345218 58.502904797 9 9.000000 0.000855354 180.066031924 -21.617744300 -21.616349141 31.228304488 10 10.000000 0.001273480 268.088528685 -21.618056502 -21.616361811 66.249216199 11 11.000000 0.001148365 241.749723441 -21.618101233 -21.616363020 65.788505557 12 12.000000 0.001337372 281.538780360 -21.618040656 -21.616360497 50.228434081 13 13.000000 0.001088173 229.078325293 -21.617815635 -21.616351586 65.527550608 14 14.000000 0.000638396 134.392771993 -21.617717647 -21.616347841 30.803143926 15 15.000000 0.001131299 238.157024534 -21.617750654 -21.616349105 30.703742482 16 16.000000 0.000882749 185.833161270 -21.618016211 -21.616359839 58.420952012 17 17.000000 0.000704309 148.268604187 -21.618111383 -21.616364232 66.953019950 18 18.000000 0.000984427 207.238102770 -21.618056478 -21.616362640 65.433037204 19 19.000000 0.001300278 273.729917837 -21.617730686 -21.616349611 66.888907175 20 20.000000 0.001251339 263.427334256 -21.617350722 -21.616332279 57.671368687 21 21.000000 0.000071510 15.053991338 -21.617118557 -21.616320874 58.848506088 22 22.000000 0.000328659 69.188061889 -21.617273411 -21.616328474 50.358033484 23 23.000000 0.001961162 412.856931729 -21.617839418 -21.616354578 65.594630019 24 24.000000 0.003432034 722.499539826 -21.618087842 -21.616363528 65.576697189 25 25.000000 0.002137357 449.948804690 -21.617944687 -21.616356561 50.318810575 26 26.000000 0.000282373 59.444052481 -21.617674167 -21.616345681 50.183309429 27 27.000000 0.001428911 300.809318861 -21.617405859 -21.616335405 50.280129558 28 28.000000 0.001230288 258.995910868 -21.617190458 -21.616327303 60.631839060 29 29.000000 0.000778815 163.953411483 -21.617239252 -21.616329041 59.914822529 30 30.000000 0.001037451 218.400572007 -21.617555040 -21.616341263 58.026954871 31 31.000000 0.000257021 54.107232870 -21.617836485 -21.616352741 63.273706142 32 32.000000 0.000815204 171.613774933 -21.617983436 -21.616358974 51.766234757 33 33.000000 0.002147387 452.060254251 -21.618044023 -21.616365491 65.707532154 34 34.000000 0.001059117 222.961601928 -21.617875727 -21.616358444 42.327060248 35 35.000000 0.000556875 117.231265217 -21.617833972 -21.616356575 38.473901298 36 36.000000 0.002660563 560.092203650 -21.617900280 -21.616359371 38.686128197 37 37.000000 0.000306512 64.525842654 -21.618022387 -21.616364623 58.028456304 38 38.000000 0.001094222 230.351784002 -21.618059911 -21.616366229 30.907870563 39 39.000000 0.002375479 500.077458607 -21.618094890 -21.616365658 65.868519638 40 40.000000 0.001059975 223.142157446 -21.617922951 -21.616358024 66.814346387 41 41.000000 0.002150347 452.683436556 -21.617727451 -21.616350173 58.576830784 42 42.000000 0.000955871 201.226516876 -21.617573183 -21.616344211 58.266955604 43 43.000000 0.003461060 728.609943461 -21.617553106 -21.616343260 81.233679124 44 44.000000 0.003689339 776.666432065 -21.617708084 -21.616348597 59.117384726 45 45.000000 0.002945410 620.057281651 -21.617936220 -21.616357146 60.046403246 46 46.000000 0.004584184 965.046120081 -21.618135902 -21.616363905 119.776386127 47 47.000000 0.001211722 255.087403714 -21.618101005 -21.616362177 80.983581299 48 48.000000 0.003172557 667.875357276 -21.618027232 -21.616358757 57.963843688 49 49.000000 0.002787604 586.836497994 -21.617921379 -21.616353596 58.793182783 50 50.000000 0.001320236 277.931380619 -21.617895704 -21.616352103 58.655742473 51 51.000000 0.001349890 284.173930376 -21.617975899 -21.616356500 81.564031711 52 52.000000 0.004197290 883.598537868 -21.618093592 -21.616362967 93.771222658 53 53.000000 0.000804420 169.343569457 -21.618143900 -21.616365817 84.571369800 54 54.000000 0.001340079 282.108729947 -21.618089714 -21.616364198 86.971021005 55 55.000000 0.001111101 233.904941648 -21.618038691 -21.616362607 65.827716856 56 56.000000 0.001635646 344.330302044 -21.618001500 -21.616361434 38.540800519 57 57.000000 0.000383350 80.701385444 -21.617996052 -21.616361311 65.489763892 58 58.000000 0.000581642 122.445243901 -21.618027478 -21.616362320 57.710738976 59 59.000000 0.000637017 134.102594542 -21.618072549 -21.616363699 57.981170168 60 60.000000 0.000256226 53.939856452 -21.618106586 -21.616364617 58.548539240 61 61.000000 0.000276851 58.281711503 -21.618134608 -21.616365048 58.458087666 62 62.000000 0.001327029 279.361436939 -21.618142721 -21.616364759 58.208439551 63 63.000000 0.000305662 64.346965320 -21.618138401 -21.616363258 57.932972059 64 64.000000 0.000792654 166.866636174 -21.618141563 -21.616362838 46.120169683 65 65.000000 0.000968894 203.968166349 -21.618163658 -21.616363286 30.770339062 66 66.000000 0.001585392 333.751027453 -21.618228272 -21.616365914 81.433016635 67 67.000000 0.003230830 680.142887167 -21.618248138 -21.616366576 57.805929371 68 68.000000 0.004550695 957.996018285 -21.618173297 -21.616364727 85.084943491 69 69.000000 0.001315308 276.894023628 -21.618119388 -21.616363118 38.600684694 70 70.000000 0.002560177 538.959267435 -21.618098609 -21.616362903 40.223963304 71 71.000000 0.001819033 382.936419195 -21.618079845 -21.616362398 90.782305011 72 72.000000 0.000517145 108.867468032 -21.618072415 -21.616363269 59.907460252 73 73.000000 0.000564062 118.744295312 -21.618059739 -21.616363893 59.481724930 74 74.000000 0.000521309 109.744026596 -21.618038633 -21.616363840 59.628348131 75 75.000000 0.002132719 448.972441454 -21.618004901 -21.616363063 61.541181826 76 76.000000 0.000535457 112.722531882 -21.617998466 -21.616362945 25.172890818 77 77.000000 0.000791883 166.704365624 -21.617996265 -21.616363155 40.223652923 78 78.000000 0.001431101 301.270260395 -21.618006814 -21.616363694 40.042347613 79 79.000000 0.001260725 265.403370341 -21.618019664 -21.616364007 39.697757854 80 80.000000 0.000110691 23.302251401 -21.618026769 -21.616364035 41.031351849 81 81.000000 0.001271648 267.702757536 -21.618039910 -21.616364022 40.622016474 82 82.000000 0.001943523 409.143432763 -21.618051808 -21.616363856 40.130044182 83 83.000000 0.002089133 439.796797555 -21.618072968 -21.616363811 59.343040636 84 84.000000 0.002634760 554.660284803 -21.618104400 -21.616364023 60.067878875 85 85.000000 0.002369065 498.727210926 -21.618147035 -21.616364725 85.188466185 86 86.000000 0.000799557 168.319960767 -21.618169688 -21.616364951 60.087728120 87 87.000000 0.001556181 327.601699012 -21.618191051 -21.616365285 59.620458533 88 88.000000 0.001500868 315.957459040 -21.618206771 -21.616365513 59.495860192 89 89.000000 0.000521386 109.760310787 -21.618210141 -21.616365465 60.615616803 90 90.000000 0.000642020 135.155667286 -21.618194752 -21.616364400 60.373461886 91 91.000000 0.000287061 60.431151866 -21.618191018 -21.616364295 24.119875298 92 92.000000 0.000548709 115.512238254 -21.618190786 -21.616364325 23.668599707 93 93.000000 0.001219521 256.729274925 -21.618195472 -21.616364513 40.134158431 94 94.000000 0.002274151 478.746167486 -21.618202538 -21.616364616 41.108107413 95 95.000000 0.002352777 495.298222687 -21.618207847 -21.616364591 40.475635013 96 96.000000 0.000042770 9.003762756 -21.618210327 -21.616364411 40.231778402 97 97.000000 0.000644745 135.729403123 -21.618213635 -21.616364382 23.213505859 98 98.000000 0.000375875 79.127780711 -21.618227316 -21.616364562 58.810299742 99 99.000000 0.002188839 460.786546096 -21.618248055 -21.616364869 60.821353728 100 100.000000 0.000810643 170.653709364 -21.618263919 -21.616365060 59.688553417 </div><div>... ... (the phenomenon looks unchanged even upon 2ps)</div><div> </div><div>Here is the input:</div><div> </div><div>&FORCE_EVAL METHOD QS &PRINT &FORCES ON &END &END &DFT BASIS_SET_FILE_NAME BASIS_MOLOPT_UCL POTENTIAL_FILE_NAME GTH_POTENTIALS &MGRID CUTOFF 400 REL_CUTOFF 60 &END MGRID &QS EPS_DEFAULT 1.0E-12 WF_INTERPOLATION ASPC &END QS &SCF SCF_GUESS RESTART MAX_SCF 500 ADDED_MOS 500 CHOLESKY INVERSE &SMEAR ON METHOD FERMI_DIRAC ELECTRONIC_TEMPERATURE [K] 300 &END SMEAR &DIAGONALIZATION ALGORITHM STANDARD &END DIAGONALIZATION &MIXING METHOD BROYDEN_MIXING ALPHA 0.1 BETA 1.5 NBROYDEN 8 &END MIXING &PRINT &RESTART ADD_LAST NUMERIC &EACH QS_SCF 0 &END EACH &END RESTART &END PRINT &END SCF &XC &XC_FUNCTIONAL &LIBXC FUNCTIONAL XC_MGGA_XC_B97M_V &END LIBXC &END XC_FUNCTIONAL &vdW_POTENTIAL DISPERSION_FUNCTIONAL NON_LOCAL &NON_LOCAL TYPE RVV10 PARAMETERS 6.0 0.01 KERNEL_FILE_NAME /usr/common/usg/cp2k/6.1/data/rVV10_kernel_table.dat &END NON_LOCAL &END vdW_POTENTIAL &XC_GRID XC_DERIV NN50_SMOOTH &END XC_GRID &END XC &END DFT &SUBSYS &CELL ABC 15.363 15.363 43.902 ALPHA_BETA_GAMMA 90.0 90.0 120. &END CELL &COORD @INCLUDE 'CO.xyz' &END COORD &KIND C BASIS_SET TZVP-MOLOPT-GTH POTENTIAL GTH-PBE-q4 &END KIND &KIND O BASIS_SET TZVP-MOLOPT-GTH POTENTIAL GTH-PBE-q6 &END KIND &END SUBSYS &END FORCE_EVAL &GLOBAL PROJECT MD_CO RUN_TYPE MD PRINT_LEVEL LOW &END GLOBAL </div><div>&MD ENSEMBLE NVT STEPS 100000 TIMESTEP 1.0 TEMPERATURE 300.0 &THERMOSTAT REGION GLOBAL TYPE CSVR &CSVR TIMECON [fs] 1. &END CSVR &END THERMOSTAT &END MD &PRINT &TRAJECTORY &EACH MD 10 &END EACH &END TRAJECTORY &RESTART &EACH MD 1 &END EACH &END RESTART &END PRINT &END MOTION </div></div> -- You received this message because you are subscribed to the Google Groups "cp2k" group. 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