Simualting time varying magnetic field

[Peela baradwaj naidu]

Hello vampire users ,

I am trying to simulate spin dynamics in CGT with a temperature pulse and under a magnetic pulse. Is there any way I can specify a time-varying magnetic pulse that starts at t = 5 ps and rises to 10 T and stays constant until the end of the simulation.

[gabo...@gmail.com]

If the temperature pulse and magnetic pulse can be simulated sequentially for your case, it might be possible using "sim:program = temperature-pulse", "sim:program = time-series", and "sim:program = field-pulse".

However, if the temperature and magnetic pulse need to be simulated simultaneously, then it might not be possible unless say you write your own "sim:program" module code for doing it.

Though, maybe someone else in the list knows a way to do it that I'm not aware of.

Regarding a time-varying magnetic pulse that rises to 10 T and stays constant until the end of the simulation, the VAMPIRE develop version [1] has "sim:program = field-pulse".  If that is used and a checkpoint is saved at the end of the simulation, then the checkpoint can be loaded to continue the simulation using the "sim:program = time-series".  With that, a resulting pulse can be seen in a plot of the output file:

All the steps used to obtain the plot with the attached files is given below:

username@computername:~/Desktop/Fe$ ls -l
total 16
-rw-r--r-- 1 username username  674 Sep 23 03:49 Fe.mat
-rw-r--r-- 1 username username 1488 Sep 23 11:14 input1
-rw-r--r-- 1 username username 1458 Sep 23 11:15 input2
-rw-r--r-- 1 username username   77 Sep 23 11:16 plotTimeField
username@computername:~/Desktop/Fe$ mv input1 input
username@computername:~/Desktop/Fe$ vampire-serial
                                                _          
                                               (_)        
                    __   ____ _ _ __ ___  _ __  _ _ __ ___
                    \ \ / / _` | '_ ` _ \| '_ \| | '__/ _ \
                     \ V / (_| | | | | | | |_) | | | |  __/
                      \_/ \__,_|_| |_| |_| .__/|_|_|  \___|
                                         | |              
                                         |_|              

                      Version 7.0.0 Dec 27 2023 21:29:33

             Git commit: fd9de813cab95bc2b2837122bd03f0238a5d2d76

  Licensed under the GNU Public License(v2). See licence file for details.

  Developers:   Richard F L Evans, Sarah Jenkins, Andrea Meo,
                Daniel Meilak, Andrew Naden, Matthew Ellis,
                Oscar Arbelaez, Sam Morris, Rory Pond, Weijia Fan,
                Phanwadee Chureemart, Pawel Sobieszczyk, Joe Barker,
                Thomas Ostler, Andreas Biternas, Roy W Chantrell,
                Wu Hong-Ye, Razvan Ababei, Sam Westmoreland,
                Milton Persson
 
                Compiled with:  GNU C++ Compiler
                Compiler Flags:

  Vampire includes a copy of the qhull library from C.B. Barber and The
  Geometry Center and may be obtained via http from www.qhull.org.

================================================================================
Mon Sep 23 11:30:30 2024
================================================================================
Initialising system variables
Creating system
Generating neighbour list..........done!
Copying system data to optimised data structures.
Using generic/normalised form of exchange interaction with 16 total interactions.
Number of atoms generated: 5488
Starting Simulation with Program field-pulse...
Simulation run time [s]: 0.413078
Simulation ended gracefully.

username@computername:~/Desktop/Fe$ mv input input1
username@computername:~/Desktop/Fe$ mv input2 input
username@computername:~/Desktop/Fe$ vampire-serial
...
Initialising system variables
Creating system
Generating neighbour list..........done!
Copying system data to optimised data structures.
Using generic/normalised form of exchange interaction with 16 total interactions.
Number of atoms generated: 5488
Starting Simulation with Program Time-Series...
Simulation run time [s]: 2.181
Simulation ended gracefully.

username@computername:~/Desktop/Fe$ gnuplot --persist plotTimeField

[1] https://github.com/richard-evans/vampire/tree/develop

Kind Regards,

Gavin

VAMPIRE user

[Christopher Johnson]

Hello, I am conducting a magnetic pulse simulation using the input file you provided and have downloaded Vampire 7.0 for this purpose. However, I encountered an error message stating: "Error - Unknown control statement 'sim:field-pulse-time' on line 35 of input file." Has this command been removed in version 7.0?

Kind Regards,

Christopher Johnson

VAMPIRE user

[Peela baradwaj naidu]

Have you tried using the develop branch ? The field pulse routine might not have been added to the main branch yet.

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[Christopher Johnson]

Thank you for your guidance. Following the adoption of the develop branch, I successfully executed the simulation.

Kind Regards,

Christopher Johnson

VAMPIRE user

[Christopher Johnson]

I have successfully reproduced the example provided above. Now, I aim to simulate a scenario where a 10 T magnetic field is applied for a period, then reduced to 0 T, mirroring the process of increasing the field from 0 T to 10 T. I attempted to modify the input file but was unable to achieve this. How should I adjust the input file to accomplish this simulation?

Kind Regards,

Christopher Johnson

VAMPIRE user

在2025年7月1日星期二 UTC+8 22:40:48<baradwa...@gmail.com> 写道：

[gabo...@gmail.com]

I'm thinking that might not be possible with only changes to the input file.

Probably, you would have to write or modify the source code for being able to do that.

I believe it would be field_pulse.cpp that you would have to make a modified version of along with possibly modifying some of the other files (e.g.,  interface.cpp) in the program folder [1] 

[1] https://github.com/richard-evans/vampire/tree/develop/src/program

Kind Regards,

Gavin

VAMPIRE user