Difference between revisions of "Ngce.m"

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{{DISPLAYTITLE:ngce.m}}
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{{DISPLAYTITLE:ngce.m}} __NOTOC__
Numerical generalised cumulant expansion route to the relaxation superoperator to second order, which is equivalent to Redfield theory.
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Numerical integral route to the Redfield relaxation superoperator.
  
 
==Syntax==
 
==Syntax==
  
     R=ngce(H,dt)
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     R=ngce(spin_system,H0,H1,dt,tau_est,reg)
  
==Arguments==
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==Parameters==
  
      H    - a cell array of spin Hamiltonian commutation
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  H0 - static laboratory frame Hamiltonian commutation su-
            superoperators obtained from an MD trajectory
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      peroperator acting in the background, a matrix
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  H1 - stochastic part (zero mean) of the laboratory frame
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      Hamiltonian commutation superoperator, a cell array
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      of matrices for each point in the MD trajectory.
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  dt - time step of the MD trajectory, seconds
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  tau_est - correlation tiume estimate for internal safety
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            control, seconds
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  reg - optional overall relaxation rate, this is added to
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        every eigenvalue of the resulting matrix to prevent
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        very small relaxation rates (e.g. singlets) from
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        jumping into positive due to integration accuracy
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        limits and then causing problems
  
      dt  - time step of the MD trajectory, seconds
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==Outputs==
  
==Outputs==
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  R  - laboratory frame relaxation superoperator
  
      R    - laboratory frame relaxation superoperator
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==Examples==
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See our recent paper with [[Jim Prestegard]]: https://doi.org/10.1016/j.jmr.2020.106891
  
 
==Notes==
 
==Notes==
The trajectory must be at least five times longer than the longest correlation time expected in the system.
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Enough trajectory points must be present to converge the ensemble averages and Redfield's integral.
  
 
==See also==
 
==See also==
[[relaxation.m]], [[lindbladian.m]], [[magpump.m]]
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[[relaxation.m]], [[lindbladian.m]], [[magpump.m]], [[adelim.m]], [[blinv.m]], [[blprod.m]], [[corrfun.m]], [[rlx_scalar.m]], [[rlx_split.m]], [[rlx_t1_t2.m]], [[sec2kite.m]], [[spden.m]], [[Kernel_utilities]]
 
 
  
''Version 2.2, authors: [[Ilya Kuprov]]''
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''Version 2.6, authors: [[Ilya Kuprov]], [[Jim Prestegard]]''

Latest revision as of 19:39, 6 June 2026

Numerical integral route to the Redfield relaxation superoperator.

Syntax

    R=ngce(spin_system,H0,H1,dt,tau_est,reg)

Parameters

 H0 - static laboratory frame Hamiltonian commutation su-
      peroperator acting in the background, a matrix

 H1 - stochastic part (zero mean) of the laboratory frame
      Hamiltonian commutation superoperator, a cell array
      of matrices for each point in the MD trajectory.

 dt - time step of the MD trajectory, seconds

 tau_est - correlation tiume estimate for internal safety
           control, seconds

 reg - optional overall relaxation rate, this is added to 
       every eigenvalue of the resulting matrix to prevent
       very small relaxation rates (e.g. singlets) from 
       jumping into positive due to integration accuracy
       limits and then causing problems

Outputs

 R  - laboratory frame relaxation superoperator

Examples

See our recent paper with Jim Prestegard: https://doi.org/10.1016/j.jmr.2020.106891

Notes

Enough trajectory points must be present to converge the ensemble averages and Redfield's integral.

See also

relaxation.m, lindbladian.m, magpump.m, adelim.m, blinv.m, blprod.m, corrfun.m, rlx_scalar.m, rlx_split.m, rlx_t1_t2.m, sec2kite.m, spden.m, Kernel_utilities

Version 2.6, authors: Ilya Kuprov, Jim Prestegard