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Re: [lammps-users] Define average density during simulation

Re: [lammps-users] Define average density during simulation

 From: alberto Date: Mon, 26 Jun 2017 22:38:03 +0200

Hi steve,
after some tests I produced average for all steps on my simulation, but I think that to produce iterative average loding per steps, I would write a function with 'sum' and 'mean' in syntax c++

Regards

Al

Il 23/giu/2017 04:49 PM, "Steve Plimpton" <sjplimp@...24...> ha scritto:
Re: your previous Q:
fix   avload all ave/time 1 100000 1
is invalid, hence the error.  See the fix ave/time doc
page about how to define those 3 numeric values.  The
last one would have to be >= 100000 in this case.

Re: your unexpected output.
I imagine you can debug this yourself
Print v_dal with thermo output.  Verify it
is what you expect at each timestep.
Then output it with fix ave/time with no averaging.
See if the values are the same.
Then expt with some averaging, and check by
hand that the values you now get are the averages
of the single timestep values.  Etc, etc.

Steve

On Fri, Jun 23, 2017 at 8:03 AM, alberto wrote:
hi,

I tried to define
variable    dal equal atoms/vol (in real units)

and

fix   avload all ave/time 1 1 1 v_dal file ave.log

in my case 100 points

the file ave.log report a wrong average

1 0.1
2 0.3
3 0.0

.

I expect that

Step.   Atoms.  Vol.  Density.   Av
1.        1.     10    0.1.     0.1
2.        3.     10    0.3.     0.2
3         0.     10     0       0.1

Av = ( 0.1+ 0.3) /2 = 0.2

I must define manually _expression_ to calculate it. I can print the results in themo_style ?

Al

2017-06-22 16:17 GMT+02:00 alberto :
Hi,

I define a variable
variable    dal equal atoms/vol
and I use fix ave/time as

fix   avload all ave/time 1 100000 1 v_dal ave one,  where 100000 is the total steps of my simulation
but I obtain message error

ERROR: Illegal fix ave/time command

Al

2017-06-21 16:20 GMT+02:00 Steve Plimpton :
The fix ave/time command can do averaging with a moving window or cummulative
ave, see its doc page and keywords.

Steve

On Tue, Jun 20, 2017 at 2:15 PM, alberto wrote:
Hi,
during a gcmc simulation, I produce density of gas per step. I would produce other column with the average density for every n-th step: for second step the average between the first and second, the third as the average between the first, the second, the third, and so on.
I'm a young user of lammps, and on manual I found the keyword fix ave/time command. It's a good idea to produce the results that I wish, or exist other procedure, or it's not possible during lammps run?

Regards

Al

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