[gmx-users] Vacuum disappear after NPT equilibration?

Justin Lemkul jalemkul at vt.edu
Fri Jan 17 19:49:04 CET 2014



On 1/17/14, 1:43 PM, Guangwei Jiang wrote:
> Dear all,
>
> I have built a system with the lipid bilayers and water molecules in the centre. Besides, two vacuum spaces above and under this target are introduced to separate the molecules flowing from the two sides.
>
> But when I start the NPT equilibration, the vacuum space gets smaller and smaller and finally disappeared. The box factors are pasted below to show the changing. Since I am new to GROMACS, can anyone tell me the reason to that and how to maintain the vacuum space?
>

In a battle between 1 atm of pressure vs. nothing, 1 atm of pressure always wins :)

If you need to maintain void space, you need to either make the box 
incompressible along the desired axis (assuming that is z in this case) or use 
NVT so the box does not change over time.

-Justin

> Thanks very much!
>
> Best wishes,
> Guangwei Jiang
>
>
> ---------------------------------------------------------------------------------------------------------------------
>
>      0    6.4184    6.4435    12.5966    0    0    0
>      0.2    6.41822    6.44332    12.5964    0    0    0
>      0.4    6.41706    6.44216    12.5958    0    0    0
>      0.6    6.41522    6.4403    12.5947    0    0    0
>      0.8    6.4129    6.43797    12.5932    0    0    0
>      1    6.41017    6.43523    12.5913    0    0    0
>      1.2    6.40754    6.4326    12.5897    0    0    0
>      1.4    6.4049    6.42994    12.588    0    0    0
>      1.6    6.40219    6.42723    12.586    0    0    0
>      1.8    6.39975    6.42478    12.5838    0    0    0
>      2    6.39724    6.42226    12.581    0    0    0
>      2.2    6.39453    6.41953    12.5779    0    0    0
>      2.4    6.39217    6.41716    12.5745    0    0    0
>      2.6    6.3902    6.41519    12.5708    0    0    0
>      2.8    6.38803    6.41301    12.5667    0    0    0
>      3    6.38594    6.41091    12.5624    0    0    0
>      3.2    6.38436    6.40933    12.5577    0    0    0
>      3.4    6.38282    6.40778    12.5528    0    0    0
>      3.6    6.38127    6.40622    12.5477    0    0    0
>      3.8    6.37971    6.40466    12.5421    0    0    0
>      4    6.37802    6.40296    12.5362    0    0    0
>      4.2    6.37659    6.40153    12.5303    0    0    0
>      4.4    6.37525    6.40018    12.5242    0    0    0
>      4.6    6.37417    6.39909    12.518    0    0    0
>      4.8    6.37328    6.3982    12.5117    0    0    0
>      5    6.37269    6.39762    12.5051    0    0    0
>      5.2    6.37259    6.39751    12.4984    0    0    0
>      5.4    6.37265    6.39757    12.4917    0    0    0
>      5.6    6.37277    6.39769    12.4847    0    0    0
>      5.8    6.37293    6.39785    12.4774    0    0    0
>      6    6.37295    6.39787    12.4699    0    0    0
>      6.2    6.37282    6.39774    12.4626    0    0    0
>      6.4    6.3721    6.39702    12.4547    0    0    0
>      6.6    6.37142    6.39633    12.4466    0    0    0
>      6.8    6.37081    6.39573    12.4381    0    0    0
>      7    6.37034    6.39525    12.4296    0    0    0
>      7.2    6.36943    6.39434    12.4208    0    0    0
>      7.4    6.36834    6.39324    12.4118    0    0    0
>      7.6    6.36681    6.39171    12.4019    0    0    0
>      7.8    6.36477    6.38966    12.3913    0    0    0
>      8    6.3625    6.38738    12.3804    0    0    0
>      8.2    6.3598    6.38468    12.3687    0    0    0
>      8.4    6.35656    6.38142    12.3561    0    0    0
>      8.6    6.35292    6.37777    12.3426    0    0    0
>      8.8    6.34929    6.37412    12.3287    0    0    0
>      9    6.34612    6.37093    12.3149    0    0    0
>      9.2    6.34322    6.36802    12.3008    0    0    0
>      9.4    6.34071    6.3655    12.2863    0    0    0
>      9.6    6.33849    6.36328    12.2715    0    0    0
>      9.8    6.33597    6.36075    12.2561    0    0    0
>      10    6.33334    6.35811    12.24    0    0    0
>      10.2    6.33147    6.35623    12.2236    0    0    0
>      10.4    6.33033    6.35508    12.2071    0    0    0
>      10.6    6.32998    6.35474    12.1908    0    0    0
>      10.8    6.32983    6.35458    12.1741    0    0    0
>      11    6.33003    6.35478    12.1575    0    0    0
>      11.2    6.33037    6.35512    12.1406    0    0    0
>      11.4    6.3304    6.35515    12.1234    0    0    0
>      11.6    6.33048    6.35523    12.1062    0    0    0
>      11.8    6.33067    6.35543    12.0889    0    0    0
>      12    6.33137    6.35613    12.0717    0    0    0
>      12.2    6.33227    6.35703    12.0542    0    0    0
>      12.4    6.33353    6.3583    12.0363    0    0    0
>      12.6    6.33458    6.35935    12.0181    0    0    0
>      12.8    6.33508    6.35985    11.9993    0    0    0
>      13    6.33507    6.35985    11.98    0    0    0
>      13.2    6.33498    6.35976    11.9604    0    0    0
>      13.4    6.33478    6.35956    11.9405    0    0    0
>      13.6    6.33366    6.35843    11.9202    0    0    0
>      13.8    6.33165    6.35642    11.8993    0    0    0
>      14    6.32908    6.35383    11.8779    0    0    0
>      14.2    6.32638    6.35112    11.8563    0    0    0
>      14.4    6.32316    6.34789    11.8341    0    0    0
>      14.6    6.3198    6.34452    11.8111    0    0    0
>      14.8    6.31646    6.34117    11.7876    0    0    0
>      15    6.31316    6.33785    11.7633    0    0    0
>      15.2    6.30998    6.33466    11.7387    0    0    0
>      15.4    6.3072    6.33187    11.7138    0    0    0
>      15.6    6.30473    6.32939    11.6885    0    0    0
>      15.8    6.30252    6.32716    11.6628    0    0    0
>      16    6.30031    6.32495    11.6368    0    0    0
>      16.2    6.29847    6.3231    11.6106    0    0    0
>      16.4    6.29721    6.32184    11.5842    0    0    0
>      16.6    6.29634    6.32096    11.5579    0    0    0
>      16.8    6.29605    6.32068    11.5314    0    0    0
>      17    6.29608    6.3207    11.5043    0    0    0
>      17.2    6.29612    6.32075    11.477    0    0    0
>      17.4    6.29627    6.3209    11.4491    0    0    0
>      17.6    6.29666    6.32129    11.4208    0    0    0
>      17.8    6.29744    6.32207    11.3924    0    0    0
>      18    6.29833    6.32296    11.3631    0    0    0
>      18.2    6.29912    6.32375    11.3328    0    0    0
>      18.4    6.29984    6.32448    11.302    0    0    0
>      18.6    6.30035    6.32498    11.2707    0    0    0
>      18.8    6.30094    6.32558    11.2394    0    0    0
>      19    6.30114    6.32578    11.208    0    0    0
>      19.2    6.3012    6.32584    11.1764    0    0    0
>      19.4    6.30137    6.32601    11.145    0    0    0
>      19.6    6.30115    6.3258    11.1131    0    0    0
>      19.8    6.30033    6.32497    11.0807    0    0    0
>      20    6.29891    6.32354    11.0474    0    0    0
>      20.2    6.29729    6.32192    11.0136    0    0    0
>      20.4    6.29577    6.32039    10.9794    0    0    0
>      20.6    6.29438    6.319    10.9451    0    0    0
>      20.8    6.29266    6.31727    10.9104    0    0    0
>      21    6.2908    6.3154    10.8754    0    0    0
>      21.2    6.28841    6.313    10.8395    0    0    0
>      21.4    6.28589    6.31047    10.8028    0    0    0
>      21.6    6.28307    6.30764    10.7654    0    0    0
>      21.8    6.28029    6.30485    10.7272    0    0    0
>      22    6.27805    6.3026    10.689    0    0    0
>      22.2    6.27554    6.30008    10.6503    0    0    0
>      22.4    6.27282    6.29735    10.6109    0    0    0
>      22.6    6.27031    6.29483    10.5713    0    0    0
>      22.8    6.26812    6.29264    10.5312    0    0    0
>      23    6.26569    6.29019    10.4911    0    0    0
>      23.2    6.26347    6.28796    10.4508    0    0    0
>      23.4    6.26137    6.28585    10.4098    0    0    0
>      23.6    6.25958    6.28406    10.3685    0    0    0
>      23.8    6.25854    6.28302    10.3275    0    0    0
>      24    6.25779    6.28226    10.2864    0    0    0
>      24.2    6.25734    6.28181    10.2449    0    0    0
>      24.4    6.25672    6.28119    10.2026    0    0    0
>      24.6    6.25577    6.28024    10.1598    0    0    0
>      24.8    6.25407    6.27853    10.1164    0    0    0
>      25    6.2518    6.27624    10.0724    0    0    0
>      25.2    6.24873    6.27316    10.0276    0    0    0
>      25.4    6.24494    6.26937    9.98188    0    0    0
>      25.6    6.24052    6.26492    9.93569    0    0    0
>      25.8    6.23596    6.26035    9.88899    0    0    0
>      26    6.23215    6.25653    9.84199    0    0    0
>      26.2    6.228    6.25236    9.79412    0    0    0
>      26.4    6.22384    6.24818    9.74592    0    0    0
>      26.6    6.21983    6.24416    9.69669    0    0    0
>      26.8    6.2159    6.2402    9.64641    0    0    0
>      27    6.21251    6.2368    9.59591    0    0    0
>      27.2    6.21031    6.23459    9.54524    0    0    0
>      27.4    6.20838    6.23266    9.49369    0    0    0
>      27.6    6.20647    6.23074    9.44129    0    0    0
>      27.8    6.20339    6.22765    9.38719    0    0    0
>      28    6.2001    6.22434    9.33221    0    0    0
>      28.2    6.19698    6.22121    9.27618    0    0    0
>      28.4    6.19443    6.21866    9.21995    0    0    0
>      28.6    6.19251    6.21673    9.16308    0    0    0
>      28.8    6.19083    6.21504    9.10538    0    0    0
>      29    6.18955    6.21375    9.04693    0    0    0
>      29.2    6.18843    6.21263    8.98765    0    0    0
>      29.4    6.1877    6.2119    8.92744    0    0    0
>      29.6    6.18717    6.21137    8.86707    0    0    0
>      29.8    6.18564    6.20983    8.80524    0    0    0
>      30    6.18351    6.20769    8.74186    0    0    0
>      30.2    6.18093    6.2051    8.67763    0    0    0
>      30.4    6.17824    6.2024    8.61307    0    0    0
>      30.6    6.17601    6.20016    8.54854    0    0    0
>      30.8    6.17444    6.19858    8.48448    0    0    0
>      31    6.17294    6.19708    8.42004    0    0    0
>      31.2    6.17164    6.19578    8.35426    0    0    0
>      31.4    6.17023    6.19436    8.28761    0    0    0
>      31.6    6.16864    6.19276    8.21973    0    0    0
>      31.8    6.167    6.19112    8.15094    0    0    0
>      32    6.16565    6.18976    8.08189    0    0    0
>      32.2    6.16394    6.18805    8.01255    0    0    0
>      32.4    6.16211    6.18621    7.94196    0    0    0
>      32.6    6.15945    6.18354    7.86984    0    0    0
>      32.8    6.15652    6.18059    7.79584    0    0    0
>      33    6.15352    6.17758    7.72051    0    0    0
>      33.2    6.15018    6.17423    7.64373    0    0    0
>      33.4    6.14602    6.17006    7.56558    0    0    0
>      33.6    6.14138    6.16539    7.4863    0    0    0
>      33.8    6.13655    6.16054    7.40553    0    0    0
>      34    6.13242    6.1564    7.32539    0    0    0
>      34.2    6.12871    6.15268    7.24498    0    0    0
>      34.4    6.12589    6.14984    7.16398    0    0    0
>      34.6    6.12426    6.14821    7.08207    0    0    0
>

-- 
==================================================

Justin A. Lemkul, Ph.D.
Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441

==================================================


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