Calculation Without Data: LBCO, CWL¶

This example shows how to calculate and plot a diffraction pattern without any measured data. Everything the calculation needs — the crystal structure, the instrument, the peak profile, and the background — is defined in code, and the pattern is computed over a calculation range instead of over loaded data points.

This is useful to preview what a candidate structure should look like, to teach, or to generate a synthetic pattern before any measurement exists. No data file is downloaded or loaded.

For this example, a constant-wavelength neutron powder experiment for La0.5Ba0.5CoO3 is used.

🛠️ Import Library¶

In [2]:

import easydiffraction as edi

import easydiffraction as edi

📦 Define Project¶

In [3]:

project = edi.Project(name='lbco_simulation')

project = edi.Project(name='lbco_simulation')

🧩 Define Structure¶

Download CIF file¶

In [4]:

structure_path = edi.download_data('struct-lbco', destination='data')

structure_path = edi.download_data('struct-lbco', destination='data')

Getting data...

Data 'struct-lbco': La0.5Ba0.5CoO3 (crystal structure)

✅ Data 'struct-lbco' downloaded to '../../../data/struct-lbco.cif'

Add Structure from CIF¶

In [5]:

project.structures.add_from_cif_path(structure_path)
project.structures.show_names()

structure = project.structures['lbco']

project.structures.add_from_cif_path(structure_path) project.structures.show_names() structure = project.structures['lbco']

Defined structures 🧩

['lbco']

Plot Structure¶

In [6]:

project.display.structure(struct_name='lbco')

project.display.structure(struct_name='lbco')

Structure 🧩 'lbco' (Atom view type: 'covalent')

Loading plot…

drag = rotate
wheel = zoom
right-drag = pan

🔬 Define Experiment¶

Create Experiment Without Data¶

Instead of loading a measured data file, the 'virtual' experiment is created directly from its type. With no measured scan present, the pattern is later computed over the data_range defined below.

In [7]:

project.experiments.create(
    name='sim',
    sample_form='powder',
    beam_mode='constant wavelength',
    radiation_probe='neutron',
)

project.experiments.create( name='sim', sample_form='powder', beam_mode='constant wavelength', radiation_probe='neutron', )

In [8]:

experiment = project.experiments['sim']

experiment = project.experiments['sim']

Set Instrument¶

In [9]:

experiment.instrument.setup_wavelength = 1.494

experiment.instrument.setup_wavelength = 1.494

Set Peak Profile¶

In [10]:

experiment.peak.broad_gauss_u = 0.1
experiment.peak.broad_gauss_v = -0.1
experiment.peak.broad_gauss_w = 0.1
experiment.peak.broad_lorentz_y = 0.1

experiment.peak.broad_gauss_u = 0.1 experiment.peak.broad_gauss_v = -0.1 experiment.peak.broad_gauss_w = 0.1 experiment.peak.broad_lorentz_y = 0.1

Set Background¶

In [11]:

experiment.background.create(id='1', position=10, intensity=20)
experiment.background.create(id='2', position=160, intensity=20)

experiment.background.create(id='1', position=10, intensity=20) experiment.background.create(id='2', position=160, intensity=20)

Set Calculation Range¶

With no measured data, the x-grid to calculate on comes from the data_range category. It already holds a sensible default window derived from the instrument, so the experiment is calculable without any setup. Here we change the default window as an example.

In [12]:

experiment.data_range.two_theta_min = 10.0
experiment.data_range.two_theta_max = 160.0
experiment.data_range.two_theta_inc = 0.05

experiment.data_range.two_theta_min = 10.0 experiment.data_range.two_theta_max = 160.0 experiment.data_range.two_theta_inc = 0.05

Set Linked Structures¶

In [13]:

experiment.linked_structures.create(structure_id='lbco', scale=10.0)

experiment.linked_structures.create(structure_id='lbco', scale=10.0)

🚀 Perform Calculation¶

Display Pattern¶

Plotting the pattern computes the calculated curve over the data_range grid and shows a two-panel view: the calculated curve with its background on the main panel, plus a Bragg-peaks row. There is no measured curve or residual, because there is no measurement.

In [14]:

project.display.pattern(expt_name='sim')

project.display.pattern(expt_name='sim')

Loading plot…

In [15]:

project.display.pattern(expt_name='sim', x_min=30, x_max=60)

project.display.pattern(expt_name='sim', x_min=30, x_max=60)

Loading plot…

Modify Parameters and Recalculate¶

In [16]:

structure.cell.length_a = 3.6
structure.atom_sites['O'].adp_iso = 1.2
experiment.peak.broad_lorentz_y = 0.9

structure.cell.length_a = 3.6 structure.atom_sites['O'].adp_iso = 1.2 experiment.peak.broad_lorentz_y = 0.9

In [17]:

project.analysis.calculate()

project.analysis.calculate()

In [18]:

project.display.pattern(expt_name='sim', x_min=30, x_max=60)

project.display.pattern(expt_name='sim', x_min=30, x_max=60)

Loading plot…

💾 Save Project¶

In [19]:

project.save_as(dir_path='projects/simulate-lbco-cwl')

project.save_as(dir_path='projects/simulate-lbco-cwl')

Saving project 📦 'lbco_simulation' to '../../../projects/simulate-lbco-cwl'

├── 📄 project.edi

├── 📁 structures/

│   └── 📄 lbco.edi

├── 📁 experiments/

│   └── 📄 sim.edi

├── 📁 analysis/

│   └── 📄 analysis.edi

└── 📁 reports/

    └── 📄 lbco_simulation.html