[RMCProfile-users] [EXTERNAL] SWAP_MULTI

[SUMMER, ARON (PGR)]

Hi Issac,

I've come across this previously, and in fact it's still a warning which prints on my latest RMC runs.

In my experience it will always print that warning to the cmd window as long as "SWAP ::" is not included in the .dat file. I've been able to safely ignore it, I suspect it's a message which wasn't updated when 'SWAP_MULTI ::' became a function.

Here is an example of a working 'SWAP_MULTI ::' section of my .dat files using RMCprofile v6.7.8. I know I'm running a version behind but I can't imagine this feature has changed.
-----------------------------------------
SWAP_MULTI ::
  > SWAP_ATOMS :: 1 2 0.15
  > SWAP_ATOMS :: 3 4 0.15
------------------------------------------

Your setup looks like about right but I am worried about the two 0.5 weightings, in my understanding that leaves no space for translations to occur leaving all your atom sites fixed, as the total probability of a swap being chosen is 1.0 with atom swaps of 1 - 2 and 3 - 4 both having a 50 % chance to occur, unless you're doing something which requires no translations, I'd recommend lowering those values.

I find keeping atom swaps at below a total of 0.4 allows the model to converge in a reasonable timeframe, and atom swaps of below 0.1 get rejected a lot resulting in very few functional swaps.

My advice would be to run with lower swap probabilities and see if any swaps get reported in the 'Refinement summary' part of the cmd output, below is an example from a 1-minute run of mine where the warning of no swaps was printed. See that 221 swaps were actually accepted, but at only half the desired probability.
-------------------------------------------------------------------------
 Refinement summary

 Move type  n(acc)     mean DX^2     p(acc)     p(gen)

 Trans.       1318       90102.0743        0.8564        0.7000
 Spin            0           0.0000             0.0000        0.0000
 Swap          221       58781.0370        0.1436        0.3000
-------------------------------------------------------------------------

Hope this helps,
Aron

________________________________
From: rmcprofile-users <rmcprofile-users-bounces at shadow.nd.rl.ac.uk> on behalf of Zhang, Yuanpeng via rmcprofile-users <rmcprofile-users at shadow.nd.rl.ac.uk>
Sent: 15 September 2022 14:36
To: rmcprofile-users at shadow.nd.rl.ac.uk <rmcprofile-users at shadow.nd.rl.ac.uk>
Cc: Zhang, Yuanpeng <zhangy3 at ornl.gov>
Subject: Re: [RMCProfile-users] [EXTERNAL] SWAP_MULTI

Hi Isaac,

It seems that the program is still reading the 'SWAP ::' section in the .dat file for some reason.

The 'SWAP_MULTI ::' for sure will work in 6.7.9 if you set it up correctly. Could you please help sharing the .dat file with me (zhangy3 at ornl.gov) so I can check?

Cheers,
Yuanpeng

--


Dr. Yuanpeng Zhang
Neutron Scattering Scientist
Spallation Neutron Source

Oak Ridge National Laboratory
1 bethel valley road, Oak Ridge, TN 37830, US
Mobile: +1(865)-335-4818
Email: zhangy3 at ornl.gov | Web: https://www.iris2020.net <https://www.iris2020.net/>

On 9/15/22, 08:20, "rmcprofile-users on behalf of Isaac Abrahams via rmcprofile-users" <rmcprofile-users-bounces at shadow.nd.rl.ac.uk on behalf of rmcprofile-users at shadow.nd.rl.ac.uk> wrote:

    Dear all

    has anyone had managed to get SWAP_MULTI :: to work in version 6.7.9?
    SWAP :: works fine but if I try to the following

    SWAP_MULTI ::
     > SWAP_ATOMS :: 1 2 0.5
     > SWAP_ATOMS :: 3 4 0.5

    I get

      No atom swap moves will be generated,
      atoms will only be translated.

    Any thoughts?

    Isaac

    _______________________________________________
    rmcprofile-users mailing list
    rmcprofile-users at rmcprofile.org
    hxxp://lists.rmcprofile.org/mailman/listinfo/rmcprofile-users


_______________________________________________
rmcprofile-users mailing list
rmcprofile-users at rmcprofile.org
http://lists.rmcprofile.org/mailman/listinfo/rmcprofile-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.rmcprofile.org/pipermail/rmcprofile-users/attachments/20220915/b9a813c4/attachment.htm>