Magic angle spinning DNP simulation.
The function returns the rotor period averaged steady state magnetization. The implementation takes a lot of inspiration from the code donated by Frederic Mentink-Vigier, please cite Fred's papers (http://dx.doi.org/10.1016/j.jmr.2015.07.001 and http://dx.doi.org/10.1016/j.jmr.2012.08.013) if you are using it.
parameters.spins - a cell array of strings listing the spins to which the parameters.offset variable refers parameters.rate - spinning rate, Hz parameters.axis - spinning axis direction vector. parameters.max_rank - rotor discretization grid rank, typically in the thousands parameters.mw_pwr - microwave power, Hz parameters.mw_frq - microwave frequency, Hz parameters.eq_time - equilibration time, seconds parameters.grid - the name of the spherical averaging grid parameters.coil - detection state parameters.verbose - set this to 1 to enable diagnostic output
The function returns the steady state population of the detection state.
A detailed walkthough for solid effect and cross effect MAS DNP is given in the example set. For a simple three-spin system discussed in Fred's paper, cross_effect_mas_enlev.m returns the rotor phase dependence of the energy levels in the system:
The energy level population dynamics during the first rotor cycle is returned by cross_effect_mas_dynam.m example:
The energy level population dynamics during the steady state rotor cycle is returned by cross_effect_mas_steady.m example:
and finally the steady state rotor-averaged, powder-averaged DNP amplitude is returned by a call to this function in cross_effect_mas_powder.m example file.
- The steep transitions visible in the figures above necessitate very large rotor grids, typically thousands of points. Our attempts at reducing this number have not been successful.
- Because DNP simulations involve strong anisotropic interactions acting for a long time, large powder averaging grids are likely to be needed. Always check that your calculation is converged with respect to the size of the spherical grid.