Download

1. Clone repository with git clone https://gitea.pkm.physik.tu-darmstadt.de/NMRRWSims/cpp.git
2. After download, change permissions of build.sh in terminal with chmod a+x build.sh

Build

Running

Command line

To run a random walk simulation Execute rwsim in the command line with

  ./rwsim /path/to/config.txt MotionModel DistributionModel --ste --spectrum -ARG1 1 -ARG2 2

It needs three positional arguments: the path to your basic configuration file (see below) and the names of the motional model and of the distribution of correlation times. Set the optional arguments --ste and/or --spectrum to create Stimulated Echos or normal echo spectra, respectively. You can overwrite any parameter given in the configuration file by adding it as optional argument with a numerical value, e.g. -TAU 1e-3 for a correlation time of 1 ms.

Configuration file config.txt

Change the values of delta, eta, mixing times, echo times,... in this file. If a paramter is defined multiple times, only the last one is used.

General parameter

This list of general parameter are necessary for all simulations:

Parameter	Description
num_walker	Number of trajectories
delta	Anisotropy parameter in Hz
eta	Asymmetry parameter

Distribution of correlation times

Two distributions are available: A delta distribution Delta, i.e. the same correlation time for every walker, and a log-normal distribution LogNormal.

• Parameters for delta distribution Delta

  Parameter	Description
  tau	Jump time in s

• Parameters for log-normal distribution LogNormal

  Parameter	Description
  tau	Maximum jump time of the distribution in s
  sigma	Standard deviation of the distribution

Motion models

Four different jump models are implemented: Isotropic random jump RandomJump, isotropic jump with a certain angle, isotropic jump with a bimodal distribution of angles, and a tetrahedral jump TetrahedralJump.

• Isotropic random jump RandomJump does not have additional parameters.

• Tetrahedral jump TetrahedralJump does not have additional parameters.

• Parameters for isotropic jump by an angle IsotropicAngle

  Parameter	Description
  angle	Jump angle in degree

• Parameters for isotropic jump with bimodal angle distribution BimodalAngle

  Parameter	Description
  angle1	First jump angle in degree
  angle2	Second jump angle in degree
  probability1	Probality that jump has angle1 (0-1)

Running

Because filenames are always the same, previous simulations and results are overwritten!

1. Execute build.sh (in terminal with ./build.sh). It compiles the source code and executes test.py