为什么我计算的均方根位移不增加?
大家好!
问个问题:为什么我计算的均方根位移不增加?
我计算的是块体金属Ir在300 K时的均方根位移,使用lammps中的 “compute msd all msd com yes”命令,发现均方根位移不随时间增加,而是随时间周期性震荡。这是什么原因呢?
我的in文件和log文件结果如下:
units metal
boundary p p p
atom_style atomic
lattice fcc 1
read_data irrh0
change_box all triclinic
pair_style eam/fs
pair_coeff * * lmpdensity20bei10001hang.eam.fs Ir Rh
velocity all create 300 49280 rot yes dist gaussian
thermo 1000
timestep 0.001
fix 1 all npt temp 300 300 0.1 x 0.0 0.0 0.5 y 0.0 0.0 0.5 z 0.0 0.0 0.5 yz 0.0 0.0 0.5 xz 0.0 0.0 0.5 xy 0.0 0.0 0.5 couple none drag 1.0
run 10000
compute msd all msd com yes
variable twopoint equal c_msd[4]/4/(step*dt+0.001*10000)
fix 9 all vector 10 c_msd[4]
variable fitslope equal slope(f_9)/4/(10*dt)
thermo_style custom step temp c_msd[1] c_msd[2] c_msd[3] c_msd[4] v_twopoint v_fitslope
run 100000
log文件结果(具体log文件见附件):
Step Temp msd[1] msd[2] msd[3] msd[4] twopoint fitslope
10000 301.89843 2.8290524e-30 2.5890064e-28 6.3875821e-32 2.6179357e-28 3.2724196e-30 2.5e+21
11000 297.42552 0.0056587552 0.0054356323 0.0050417289 0.016136116 0.00019209662 0.0077686093
12000 301.84951 0.0060977739 0.0049348668 0.0052455045 0.016278145 0.00018497892 0.0040012759
13000 300.04116 0.0070037489 0.0048961463 0.0052273452 0.01712724 0.00018616566 0.0026591218
14000 298.23623 0.0079874161 0.0056067162 0.0054528389 0.019046971 0.00019840595 0.00206093
15000 299.69843 0.0062998502 0.0049096236 0.0053625497 0.016572024 0.00016572024 0.0016898664
16000 300.07968 0.0056144742 0.0052758157 0.0047723182 0.015662608 0.000150602 0.0013932409
17000 301.45262 0.0079681822 0.0052612288 0.0050407475 0.018270158 0.00016916813 0.0011904743
18000 301.80347 0.0060978238 0.004971777 0.0051563989 0.016226 0.000144875 0.0010402451
19000 301.66477 0.0072145951 0.0054426425 0.005095153 0.017752391 0.00015303785 0.00092011832
20000 299.61863 0.007698821 0.0052012635 0.0054214609 0.018321545 0.00015267955 0.00083398482
21000 300.68272 0.0063881825 0.0051862235 0.0054230375 0.016997444 0.00013707616 0.00076503599
22000 298.83271 0.0047736189 0.0053384006 0.0049477729 0.015059792 0.00011765463 0.00069937582
23000 300.45892 0.0056389628 0.0050950377 0.0049827681 0.015716769 0.00011906643 0.00064221439
24000 303.62227 0.007398674 0.0049974266 0.0052721434 0.017668244 0.00012991356 0.0005965328
25000 299.84307 0.0061494073 0.0054771373 0.0049857567 0.016612301 0.0001186593 0.00055533919
26000 301.55517 0.007299623 0.0051771214 0.0052031874 0.017679932 0.0001227773 0.00052056641
27000 298.26732 0.0069209022 0.0055738288 0.0056839288 0.01817866 0.00012282878 0.00049250409
28000 300.08814 0.0062397018 0.0052447814 0.005098513 0.016582996 0.00010909866 0.00046449839
29000 300.14209 0.006982715 0.00503399 0.0050015016 0.017018207 0.00010909107 0.00043842533
30000 300.75248 0.0055341589 0.0055658925 0.0053996513 0.016499703 0.00010312314 0.00041711989
31000 296.53093 0.0061001289 0.0050080568 0.0048483889 0.015956575 9.7296186e-05 0.00039695961
32000 299.87248 0.0073760041 0.0050354061 0.0050429774 0.017454388 0.00010389516 0.0003791721
33000 299.66484 0.0073484239 0.0053788324 0.0057623046 0.018489561 0.00010749745 0.00036459916
34000 300.07601 0.0049186558 0.0051259282 0.0052348453 0.015279429 8.6814939e-05 0.00034930673
35000 299.87286 0.0064086615 0.0061884715 0.004877802 0.017474935 9.7082973e-05 0.00033460758
36000 299.84434 0.0066646094 0.0048294909 0.0053159849 0.016810085 9.1359159e-05 0.00032165627
37000 297.91899 0.0061680714 0.0050030814 0.004837319 0.016008472 8.5151446e-05 0.00030928358
38000 300.91479 0.0071706309 0.0054941004 0.0049346768 0.017599408 9.1663584e-05 0.00029844342
39000 300.44247 0.0078278338 0.005059229 0.0054810804 0.018368143 9.3715016e-05 0.00028909774
40000 301.09965 0.005983152 0.0057060163 0.0052567033 0.016945872 8.4729358e-05 0.00027969696
41000 301.70082 0.005213601 0.0049187698 0.004959821 0.015092192 7.3981333e-05 0.00027014223
42000 301.19422 0.0054678732 0.004984567 0.005088072 0.015540512 7.4714001e-05 0.00026132728
43000 300.91401 0.0052599669 0.0051724485 0.0048738762 0.015306292 7.2199489e-05 0.00025320055
44000 302.05789 0.0070400607 0.0048502342 0.0050042656 0.01689456 7.8215558e-05 0.00024557821
45000 298.97062 0.007746407 0.0050231401 0.0056500479 0.018419595 8.3725432e-05 0.0002390822
46000 300.05007 0.0051977939 0.0055103185 0.0055031092 0.016211222 7.2371525e-05 0.00023282463
47000 299.4236 0.0048297706 0.0047548567 0.0048374515 0.014422079 6.3254732e-05 0.00022611616
48000 301.05959 0.0062508005 0.0056532827 0.0053117831 0.017215866 7.420632e-05 0.00021994267
49000 298.22135 0.0055343483 0.0050281565 0.0048554094 0.015417914 6.5330145e-05 0.00021424059
50000 300.80348 0.0064247985 0.0048178211 0.0050688606 0.01631148 6.7964501e-05 0.00020867841
51000 296.95482 0.0075531567 0.0057532794 0.0059831052 0.019289541 7.9055497e-05 0.00020409138
52000 300.04882 0.0057057603 0.0049493562 0.0057273017 0.016382418 6.6058138e-05 0.00019960339
53000 304.99884 0.0057889852 0.0052041512 0.0051179738 0.01611111 6.3932977e-05 0.00019475509
54000 300.80813 0.0062859607 0.0053011765 0.0050725702 0.016659707 6.5076982e-05 0.00019031833
55000 300.25049 0.0088046465 0.0051237551 0.0050964652 0.019024867 7.3172564e-05 0.00018609576
56000 300.91853 0.0067657153 0.0054476446 0.004765334 0.016978694 6.4313234e-05 0.00018195944
57000 298.92289 0.0070387719 0.005045254 0.0052889377 0.017372964 6.4824491e-05 0.00017829227
58000 302.3328 0.0059156097 0.0050074463 0.0058129192 0.016735975 6.1529321e-05 0.00017477277
59000 303.56617 0.005638244 0.0051978321 0.0048559013 0.015691977 5.685499e-05 0.00017103567
60000 298.85958 0.0063556119 0.0053571167 0.0049554058 0.016668134 5.9529051e-05 0.00016740028
61000 298.97054 0.0056809854 0.0054287363 0.0051406352 0.016250357 5.7219567e-05 0.00016403003
62000 299.8487 0.0060650946 0.0053198497 0.0049653914 0.016350336 5.6771999e-05 0.00016078662
63000 298.79745 0.0072017075 0.0050468402 0.0053879308 0.017636479 6.0398899e-05 0.00015779035
64000 298.52725 0.0065339645 0.0052869974 0.0060880706 0.017909033 6.0503488e-05 0.00015510154
65000 299.0601 0.0048691658 0.0049442197 0.0053330828 0.015146468 5.0488228e-05 0.00015223456
66000 304.27773 0.005227859 0.0047804533 0.0047017478 0.01471006 4.8388356e-05 0.00014928503
67000 298.60406 0.0055386438 0.0050697796 0.0051916612 0.015800085 5.1298976e-05 0.00014665091
68000 294.77097 0.0068714679 0.0048023858 0.0051835387 0.016857392 5.4030104e-05 0.00014400882
69000 301.01698 0.0071880926 0.0052064358 0.0051995217 0.01759405 5.5677374e-05 0.00014154834
70000 297.98589 0.0070270906 0.0050506417 0.0058015154 0.017879248 5.5872649e-05 0.00013938726
71000 299.43637 0.006461771 0.0049475992 0.005186069 0.016595439 5.1220491e-05 0.00013706437
72000 298.46606 0.0073150955 0.005392429 0.0049643888 0.017671913 5.3877784e-05 0.00013475848
73000 301.59174 0.0058575857 0.004875961 0.0049376851 0.015671232 4.7202505e-05 0.00013263855
74000 302.43501 0.0055100482 0.0048817303 0.0049516749 0.015343453 4.566504e-05 0.00013043447
75000 299.22423 0.0068288818 0.0055293058 0.0051719773 0.017530165 5.1559309e-05 0.00012844652
76000 297.28429 0.007069468 0.005203601 0.0056469038 0.017919973 5.2092944e-05 0.00012662826
77000 297.08123 0.0061076845 0.0053248595 0.0055070034 0.016939547 4.867686e-05 0.00012475979
78000 301.02881 0.0057644528 0.0047521723 0.0049413534 0.015457978 4.3914712e-05 0.00012291269
79000 299.15898 0.0065242747 0.0048221239 0.005114398 0.016460797 4.6238192e-05 0.00012113719
80000 299.17317 0.0056670981 0.0056201812 0.0048883185 0.016175598 4.4932216e-05 0.00011933602
81000 295.82973 0.0077252212 0.0045996787 0.0050737996 0.017398699 4.7798625e-05 0.00011769021
82000 297.61492 0.0073337206 0.0050115039 0.005623591 0.017968815 4.8828303e-05 0.0001161671
83000 301.18737 0.0064195266 0.0051314681 0.0052360076 0.016787002 4.512635e-05 0.00011465058
84000 297.58204 0.0064266142 0.00470375 0.0047966194 0.015926984 4.2358999e-05 0.00011305679
85000 301.92668 0.0066293484 0.00564057 0.0050907555 0.017360674 4.5685984e-05 0.00011161073
86000 298.97242 0.0051731846 0.0049469084 0.0046981204 0.014818214 3.8589098e-05 0.0001101049
87000 299.56973 0.0067744293 0.0047183529 0.0051869596 0.016679742 4.2989025e-05 0.00010863311
88000 300.18744 0.0076201293 0.0053130539 0.0060045202 0.018937703 4.8310468e-05 0.00010736296
89000 302.77351 0.0053788508 0.0050013357 0.0055387726 0.015918959 4.0199392e-05 0.00010603751
90000 300.82973 0.0054375773 0.0054304414 0.0051943992 0.016062418 4.0156045e-05 0.00010464501
91000 299.99311 0.0076417013 0.005178455 0.0053530656 0.018173222 4.4983223e-05 0.00010338704
92000 302.04881 0.005428566 0.0048461922 0.0046507396 0.014925498 3.6582102e-05 0.00010207711
93000 298.95524 0.0068301059 0.0056344797 0.0049680145 0.0174326 4.2312136e-05 0.00010079171
94000 295.46411 0.0072494516 0.0051635885 0.0054999338 0.017912974 4.3060033e-05 9.9674907e-05
95000 299.81099 0.0054141667 0.0049052212 0.0055957441 0.015915132 3.7893171e-05 9.853555e-05
96000 297.71331 0.005077124 0.0053964101 0.0049655797 0.015439114 3.6413004e-05 9.7375386e-05
97000 300.63632 0.0078719911 0.00520438 0.0054411566 0.018517528 4.3265252e-05 9.6264624e-05
98000 298.97708 0.0047826843 0.0052480462 0.004992146 0.015022876 3.4775177e-05 9.5129667e-05
99000 295.7821 0.0060173991 0.0049712524 0.0052657476 0.016254399 3.7280732e-05 9.4004765e-05
100000 299.60525 0.0075057344 0.0050236901 0.005305359 0.017834784 4.0533599e-05 9.2971842e-05
101000 298.74362 0.006510655 0.0053273215 0.005400958 0.017238934 3.8826429e-05 9.2000182e-05
102000 302.35778 0.0046330963 0.0048327217 0.0049176211 0.014383439 3.2105891e-05 9.0958877e-05
103000 300.93311 0.0051896854 0.0049992797 0.0053868911 0.015575856 3.4459859e-05 8.9937122e-05
104000 296.48185 0.0055887292 0.0052950405 0.004855635 0.015739405 3.4516238e-05 8.8958987e-05
105000 294.55858 0.006060387 0.0051071599 0.0051691074 0.016336654 3.5514466e-05 8.7953279e-05
106000 299.39832 0.0071706577 0.0053263969 0.005378465 0.01787552 3.8524827e-05 8.7054319e-05
107000 293.74344 0.0063445553 0.004893631 0.0055199519 0.016758138 3.5807987e-05 8.6211446e-05
108000 299.66338 0.0052864881 0.0048236316 0.0053303682 0.015440488 3.2712898e-05 8.5292749e-05
109000 299.9327 0.0065405297 0.0053890281 0.0051594737 0.017089031 3.5901327e-05 8.4408783e-05
110000 301.82442 0.0072875544 0.0048005117 0.0049638849 0.017051951 3.5524898e-05 8.3545512e-05
固体原子又不扩散,msd为什么要增加?下次不要给这种数据,请画图展示。
谢谢你的指点!
不过,固体的原子的均方根位移不会随时间增长吗?附件图是我画的整个体系的均方根位移随时间的变化图,图中没看到均方根位移增长,只有震荡。
Graph3.jpg
,
固体原子的均方位移怎么会增加?增加代表在扩散,还懂啊?
当温度增加时,固体原子的均方位移会不会增加呢?或者掺杂了其它溶质原子,均方位移会不会增加呢?
请问下楼主,分析均方根位移的目的是什么呢?判断体系平衡?还是说验证模型的合理性?