SimPYson: A Pythonic Interface for SIMPSON

SimPYson is a Python package that makes it easier to work with SIMPSON, a code for simulating solid-state NMR experiments. It handles preparing input files from DFT calculations, running simulations, and reading results — all from Python.

Features

• Run SIMPSON simulations from Python: Use simulate_spectrum() for smart defaults or SimpCalc for full control over spin systems, pulse sequences, and output.
• Convert DFT data to SIMPSON input files: Prepare spin systems from CASTEP, Quantum Espresso, and VASP calculations via ASE and Soprano.
• Read SIMPSON output files: Load .spe, .fid, .xreim, and .csdf files into a unified Simpy object with automatic FID↔spectrum conversion and ppm scaling.
• Pulse sequence templates: Built-in templates for no-pulse, 90° pulse, and CPMAS experiments. Custom Tcl sequences are also supported.
• Graphical User Interface: Launch with simpyson gui to inspect and process spectra without any coding.

Quick Start

Read a SIMPSON output file:

from simpyson import read_simp

data = read_simp("ethanol.spe", b0="400MHz", nucleus="1H")
print(data.ppm['ppm'])   # ppm axis, auto-calculated
print(data.spe['hz'])    # Hz axis

Accessing .fid on a spectrum file (or .spe on a FID) triggers automatic conversion via FFT — no manual processing needed.

Simulate a spectrum directly from Python:

from simpyson import simulate_spectrum

spinsys = """
channels 13C
nuclei 13C 13C
shift 1 10p 0 0 0 0 0
shift 2 50p 0 0 0 0 0
"""

result = simulate_spectrum(spinsys, proton_frequency=400e6, spin_rate=10000)
print(result.ppm['ppm'])

simulate_spectrum() automatically estimates the spectral width and carrier offset from the chemical shifts. For full control over all parameters, use SimpCalc directly — see the documentation.

Installation

pip install git+https://github.com/nuts-org/simpyson.git

Requires Python ≥ 3.10 and a working SIMPSON installation for running simulations.

Documentation

Full documentation and tutorials are available at nuts-org.github.io/simpyson.

Planned Features

• Additional pulse sequence templates for more complex NMR experiments.
• Broader support for DFT codes — suggestions welcome.