Re: [AMBER] A problem about periodic box dimensions happens to Tutorial 1.7

From: wangwei1669 <wangwei1669.126.com>
Date: Sun, 5 Sep 2021 16:49:14 +0800 (CST)

Hi, David,


Thanks for your concern. Here is the summarized table of MD result.


|

|
|

|

Min

|

Heat 1

|

Heat 2

|

Hold 1

|

Hold 10

|

Prod

|
|

Boundary conditions

|

Fixed volume

|

Fixed volume

|

Fixed pressure

|

Fixed pressure

|

Fixed pressure

|

Fixed pressure

|
|

Time passed (ps)

|

|

5

|

105

|

605

|

5105

|

81065

|
|

Temperature (K)

|

|

79.85

|

303.12

|

302.11

|

302.28

|

303.76

|
|

Energy

|

-79223

|

-63868

|

-30791

|

-36063

|

-35981

|

-35987

|
|

Volume

|

|

|

358514

|

304944

|

303957

|

304187

|
|

Density

|

|

|

0.8644

|

1.0162

|

1.0195

|

1.0187

|
| | | | |


I am not familiar with how to analyze the trajectory file by cpptraj. So I extract some data from output file.
I don't know why there are larger density and smaller volume recorded after 600 ps than those at 105 ps. I see the systems dramatically enlarging after 105 ps (hold and production).
Should I change the boundary condition to fix the volume instead of the pressure at these two stage?
And I also concern that I sourced ff14SB force field instead of ff12SB that used in tutorial web since I did not find it. Does this significantly influence the result?


Best regards,
Wang Wei





At 2021-09-04 19:57:34, "David A Case" <dacase1.gmail.com> wrote:
>On Sat, Sep 04, 2021, wangwei1669 wrote:
>>
>>When I was following the production step of tutorial 1.7 "An Amber Lipid
>>Force Field Tutorial: Lipid14", I encountered a error about periodic box
>>dimensions.
>>
>>"Lipid production 303K 125ns
>> ntb=2, ! Constant pressure periodic boundary conditions
>> ntp=2, ! Anisotropic pressure coupling
>>The simulation stopped at 80 ns and I received a feedback:
>>
>>
>>"ERROR: Calculation halted. Periodic box dimensions have changed too much
>>from their initial values.
>
>What does the density vs time profile for your simulation look like? Have
>the box dimensions indeed changed by a lot? Or, is there any indication of
>an instability (sudden change in energy, etc.)? It is rather unusual to see
>such behavior after 80 ns of simulation, but I'm not a lipid14 user.
>
>....dac
>
>
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Received on Sun Sep 05 2021 - 02:00:02 PDT
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