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Albite, ²⁷Al (I=5/2) 3QMAS¶
²⁷Al (I=5/2) triple-quantum magic-angle spinning (3Q-MAS) simulation.
The following is an example of \(^{27}\text{Al}\) 3QMAS simulation of albite \(\text{NaSi}_3\text{AlO}_8\). The \(^{27}\text{Al}\) tensor parameters were obtained from Massiot et al. [1].
import matplotlib.pyplot as plt
from mrsimulator import Simulator, SpinSystem, Site
from mrsimulator.method.lib import ThreeQ_VAS
from mrsimulator import signal_processor as sp
from mrsimulator.spin_system.tensors import SymmetricTensor
from mrsimulator.method import SpectralDimension
Generate the site and spin system objects.
site = Site(
isotope="27Al",
isotropic_chemical_shift=64.7, # in ppm
quadrupolar=SymmetricTensor(Cq=3.25e6, eta=0.68), # Cq is in Hz
)
spin_systems = [SpinSystem(sites=[site])]
Select a Triple Quantum variable-angle spinning method. You may optionally provide a rotor_angle to the method. The default rotor_angle is the magic-angle.
method = ThreeQ_VAS(
channels=["27Al"],
magnetic_flux_density=7, # in T
spectral_dimensions=[
SpectralDimension(
count=256,
spectral_width=1e4, # in Hz
reference_offset=-3e3, # in Hz
label="Isotropic dimension",
),
SpectralDimension(
count=512,
spectral_width=1e4, # in Hz
reference_offset=4e3, # in Hz
label="MAS dimension",
),
],
)
Create the Simulator object, add the method and spin system objects, and run the simulation.
The plot of the simulation.
dataset = sim.methods[0].simulation
plt.figure(figsize=(4.25, 3.0))
ax = plt.subplot(projection="csdm")
cb = ax.imshow(dataset.real / dataset.real.max(), aspect="auto", cmap="gist_ncar_r")
plt.colorbar(cb)
ax.invert_xaxis()
ax.invert_yaxis()
plt.tight_layout()
plt.show()
Add post-simulation signal processing.
processor = sp.SignalProcessor(
operations=[
# Gaussian convolution along both dimensions.
sp.IFFT(dim_index=(0, 1)),
sp.apodization.Gaussian(FWHM="0.2 kHz", dim_index=0),
sp.apodization.Gaussian(FWHM="0.2 kHz", dim_index=1),
sp.FFT(dim_index=(0, 1)),
]
)
processed_dataset = processor.apply_operations(dataset=sim.methods[0].simulation)
processed_dataset /= processed_dataset.max()
The plot of the simulation after signal processing.
plt.figure(figsize=(4.25, 3.0))
ax = plt.subplot(projection="csdm")
cb = ax.imshow(processed_dataset.real, cmap="gist_ncar_r", aspect="auto")
plt.colorbar(cb)
ax.set_xlim(75, 25)
ax.set_ylim(-15, -65)
plt.tight_layout()
plt.show()
Total running time of the script: (0 minutes 0.877 seconds)