Parameters

The data analysis process, introduced in the Concept section, uses parameters to describe structures, experiments, and the analysis state.

Each parameter has:

a Python access path used in notebooks and scripts,
an Edi key used when EasyDiffraction saves a project, and
where applicable, a CIF key used for importing crystallographic data or writing IUCr/pdCIF reports.

Edi is the regular EasyDiffraction project persistence format. CIF remains important for crystallographic input and for strict report exports. The tables below therefore separate code access, Edi keys, and CIF keys instead of treating one name as universal.

Parameter Attributes

Parameters in EasyDiffraction are objects. Alongside name and value, they can carry attributes such as uncertainty, unit, minimum and maximum allowed values, and fit bounds. The most important day-to-day attribute is free, which controls whether a parameter is refined during fitting. It is False by default.

Users normally access parameters through top-level objects such as project, structures, and experiments; parameters are created when the project objects are created or loaded.

Important

Parameters are accessed through their parent objects. For example, if a structure has the ID nacl, the space-group name is accessed as:

project.structures['nacl'].space_group.name_h_m

For compactness, the code tables show only the last part of the access path, such as space_group.name_h_m.

Structure Parameters

Crystal Structure Parameters

pd-neut-cwl pd-neut-tof pd-xray sc-neut-cwl

How to access in the codeKeys in EdiKeys in CIF

Category	Parameter	How to access in the code
space_group	name_h_m	space_group.name_h_m
	coord_system_code	space_group.coord_system_code
cell	length_a	cell.length_a
	length_b	cell.length_b
	length_c	cell.length_c
	angle_alpha	cell.angle_alpha
	angle_beta	cell.angle_beta
	angle_gamma	cell.angle_gamma
atom_site	id	atom_sites['ID'].id
	type_symbol	atom_sites['ID'].type_symbol
	fract_x	atom_sites['ID'].fract_x
	fract_y	atom_sites['ID'].fract_y
	fract_z	atom_sites['ID'].fract_z
	occupancy	atom_sites['ID'].occupancy
	adp_type	atom_sites['ID'].adp_type
	adp_iso	atom_sites['ID'].adp_iso
	multiplicity	atom_sites['ID'].multiplicity
	wyckoff_letter	atom_sites['ID'].wyckoff_letter

Category	Parameter	Key in Edi
space_group	name_h_m	`_space_group.name_h_m`
	coord_system_code	`_space_group.coord_system_code`
cell	length_a	`_cell.length_a`
	length_b	`_cell.length_b`
	length_c	`_cell.length_c`
	angle_alpha	`_cell.angle_alpha`
	angle_beta	`_cell.angle_beta`
	angle_gamma	`_cell.angle_gamma`
atom_site	id	`_atom_site.id`
	type_symbol	`_atom_site.type_symbol`
	fract_x	`_atom_site.fract_x`
	fract_y	`_atom_site.fract_y`
	fract_z	`_atom_site.fract_z`
	occupancy	`_atom_site.occupancy`
	adp_type	`_atom_site.adp_type`
	adp_iso	`_atom_site.adp_iso`
	multiplicity	`_atom_site.multiplicity`
	wyckoff_letter	`_atom_site.wyckoff_letter`

Category	Parameter	Key in CIF	CIF dictionary
space_group	name_h_m	`_space_group.name_H-M_alt`	coreCIF
	coord_system_code	`_space_group.IT_coordinate_system_code`	coreCIF
cell	length_a	`_cell.length_a`	coreCIF
	length_b	`_cell.length_b`	coreCIF
	length_c	`_cell.length_c`	coreCIF
	angle_alpha	`_cell.angle_alpha`	coreCIF
	angle_beta	`_cell.angle_beta`	coreCIF
	angle_gamma	`_cell.angle_gamma`	coreCIF
atom_site	id	`_atom_site.label`	coreCIF
	type_symbol	`_atom_site.type_symbol`	coreCIF
	fract_x	`_atom_site.fract_x`	coreCIF
	fract_y	`_atom_site.fract_y`	coreCIF
	fract_z	`_atom_site.fract_z`	coreCIF
	occupancy	`_atom_site.occupancy`	coreCIF
	adp_type	`_atom_site.ADP_type`	coreCIF
	adp_iso	`_atom_site.B_iso_or_equiv`	coreCIF
	multiplicity	`_atom_site.site_symmetry_multiplicity`	coreCIF
	wyckoff_letter	`_atom_site.Wyckoff_symbol`	coreCIF

Experiment Parameters

Common Parameters

pd-neut-cwl pd-neut-tof pd-xray sc-neut-cwl

How to access in the codeKeys in EdiKeys in CIF

Category	Parameter	How to access in the code
experiment_type	beam_mode	experiment_type.beam_mode
	radiation_probe	experiment_type.radiation_probe
	sample_form	experiment_type.sample_form
	scattering_type	experiment_type.scattering_type

Category	Parameter	Key in Edi
experiment_type	beam_mode	`_experiment_type.beam_mode`
	radiation_probe	`_experiment_type.radiation_probe`
	sample_form	`_experiment_type.sample_form`
	scattering_type	`_experiment_type.scattering_type`

Category	Parameter	Key in CIF	CIF dictionary
experiment_type	beam_mode	`_easydiffraction_experiment_type.beam_mode`	coreCIF
	radiation_probe	`_easydiffraction_experiment_type.radiation_probe`	coreCIF
	sample_form	`_easydiffraction_experiment_type.sample_form`	coreCIF
	scattering_type	`_easydiffraction_experiment_type.scattering_type`	coreCIF

Standard Powder Diffraction

pd-neut-cwl pd-neut-tof pd-xray

How to access in the codeKeys in EdiKeys in CIF

Category	Parameter	How to access in the code
background	position	background.position
	intensity	background.intensity
	order	background.order
	coef	background.coef
linked_structure	structure_id	linked_structures['ID'].structure_id
	scale	linked_structures['ID'].scale
preferred_orientation	structure_id	preferred_orientation['ID'].structure_id
	march_r	preferred_orientation['ID'].march_r
	march_random_fract	preferred_orientation['ID'].march_random_fract
	index_h	preferred_orientation['ID'].index_h
	index_k	preferred_orientation['ID'].index_k
	index_l	preferred_orientation['ID'].index_l

Category	Parameter	Key in Edi
background	position	`_background.position`
	intensity	`_background.intensity`
	order	`_background.order`
	coef	`_background.coef`
linked_structure	structure_id	`_linked_structure.structure_id`
	scale	`_linked_structure.scale`
preferred_orientation	structure_id	`_preferred_orientation.structure_id`
	march_r	`_preferred_orientation.march_r`
	march_random_fract	`_preferred_orientation.march_random_fract`
	index_h	`_preferred_orientation.index_h`
	index_k	`_preferred_orientation.index_k`
	index_l	`_preferred_orientation.index_l`

Category	Parameter	Key in CIF	CIF dictionary
background	position	`_pd_background.line_segment_X`	pdCIF
	intensity	`_pd_background.line_segment_intensity`	pdCIF
	order	`_pd_background.Chebyshev_order`	pdCIF
	coef	`_pd_background.Chebyshev_coef`	pdCIF
linked_structure	structure_id	`_pd_phase_block.id`	pdCIF
	scale	`_pd_phase_block.scale`	pdCIF
preferred_orientation	structure_id	`_pd_pref_orient_March_Dollase.phase_id`	pdCIF
	march_r	`_pd_pref_orient_March_Dollase.r`	pdCIF
	march_random_fract	`_easydiffraction_pref_orient.march_random_fract`	coreCIF
	index_h	`_pd_pref_orient_March_Dollase.index_h`	pdCIF
	index_k	`_pd_pref_orient_March_Dollase.index_k`	pdCIF
	index_l	`_pd_pref_orient_March_Dollase.index_l`	pdCIF

pd-neut-cwl pd-xray

How to access in the codeKeys in EdiKeys in CIF

Category	Parameter	How to access in the code
instrument	setup_wavelength	instrument.setup_wavelength
	calib_twotheta_offset	instrument.calib_twotheta_offset
peak	broad_gauss_u	peak.broad_gauss_u
	broad_gauss_v	peak.broad_gauss_v
	broad_gauss_w	peak.broad_gauss_w
	broad_lorentz_x	peak.broad_lorentz_x
	broad_lorentz_y	peak.broad_lorentz_y

Category	Parameter	Key in Edi
instrument	setup_wavelength	`_instrument.setup_wavelength`
	calib_twotheta_offset	`_instrument.calib_twotheta_offset`
peak	broad_gauss_u	`_peak.broad_gauss_u`
	broad_gauss_v	`_peak.broad_gauss_v`
	broad_gauss_w	`_peak.broad_gauss_w`
	broad_lorentz_x	`_peak.broad_lorentz_x`
	broad_lorentz_y	`_peak.broad_lorentz_y`

Category	Parameter	Key in CIF	CIF dictionary
instrument	setup_wavelength	`_diffrn_radiation_wavelength.value`	coreCIF
	calib_twotheta_offset	`_pd_calib.2theta_offset`	pdCIF
peak	broad_gauss_u	`_easydiffraction_peak.broad_gauss_u`	coreCIF
	broad_gauss_v	`_easydiffraction_peak.broad_gauss_v`	coreCIF
	broad_gauss_w	`_easydiffraction_peak.broad_gauss_w`	coreCIF
	broad_lorentz_x	`_easydiffraction_peak.broad_lorentz_x`	coreCIF
	broad_lorentz_y	`_easydiffraction_peak.broad_lorentz_y`	coreCIF

pd-neut-tof

How to access in the codeKeys in EdiKeys in CIF

Category	Parameter	How to access in the code
instrument	setup_twotheta_bank	instrument.setup_twotheta_bank
	calib_d_to_tof_reciprocal	instrument.calib_d_to_tof_reciprocal
	calib_d_to_tof_offset	instrument.calib_d_to_tof_offset
	calib_d_to_tof_linear	instrument.calib_d_to_tof_linear
	calib_d_to_tof_quadratic	instrument.calib_d_to_tof_quadratic
peak	broad_gauss_sigma_0	peak.broad_gauss_sigma_0
	broad_gauss_sigma_1	peak.broad_gauss_sigma_1
	broad_gauss_sigma_2	peak.broad_gauss_sigma_2
	broad_lorentz_gamma_0	peak.broad_lorentz_gamma_0
	broad_lorentz_gamma_1	peak.broad_lorentz_gamma_1
	broad_lorentz_gamma_2	peak.broad_lorentz_gamma_2
	decay_beta_0	peak.decay_beta_0
	decay_beta_1	peak.decay_beta_1
	rise_alpha_0	peak.rise_alpha_0
	rise_alpha_1	peak.rise_alpha_1

Category	Parameter	Key in Edi
instrument	setup_twotheta_bank	`_instrument.setup_twotheta_bank`
	calib_d_to_tof_reciprocal	`_instrument.calib_d_to_tof_reciprocal`
	calib_d_to_tof_offset	`_instrument.calib_d_to_tof_offset`
	calib_d_to_tof_linear	`_instrument.calib_d_to_tof_linear`
	calib_d_to_tof_quadratic	`_instrument.calib_d_to_tof_quadratic`
peak	broad_gauss_sigma_0	`_peak.broad_gauss_sigma_0`
	broad_gauss_sigma_1	`_peak.broad_gauss_sigma_1`
	broad_gauss_sigma_2	`_peak.broad_gauss_sigma_2`
	broad_lorentz_gamma_0	`_peak.broad_lorentz_gamma_0`
	broad_lorentz_gamma_1	`_peak.broad_lorentz_gamma_1`
	broad_lorentz_gamma_2	`_peak.broad_lorentz_gamma_2`
	decay_beta_0	`_peak.decay_beta_0`
	decay_beta_1	`_peak.decay_beta_1`
	rise_alpha_0	`_peak.rise_alpha_0`
	rise_alpha_1	`_peak.rise_alpha_1`

Category	Parameter	Key in CIF	CIF dictionary
instrument	setup_twotheta_bank	`_instr.2theta_bank`	coreCIF
	calib_d_to_tof_reciprocal	`_instr.d_to_tof_recip`	coreCIF
	calib_d_to_tof_offset	`_instr.d_to_tof_offset`	coreCIF
	calib_d_to_tof_linear	`_instr.d_to_tof_linear`	coreCIF
	calib_d_to_tof_quadratic	`_instr.d_to_tof_quad`	coreCIF
peak	broad_gauss_sigma_0	`_easydiffraction_peak.gauss_sigma_0`	coreCIF
	broad_gauss_sigma_1	`_easydiffraction_peak.gauss_sigma_1`	coreCIF
	broad_gauss_sigma_2	`_easydiffraction_peak.gauss_sigma_2`	coreCIF
	broad_lorentz_gamma_0	`_easydiffraction_peak.lorentz_gamma_0`	coreCIF
	broad_lorentz_gamma_1	`_easydiffraction_peak.lorentz_gamma_1`	coreCIF
	broad_lorentz_gamma_2	`_easydiffraction_peak.lorentz_gamma_2`	coreCIF
	decay_beta_0	`_easydiffraction_peak.decay_beta_0`	coreCIF
	decay_beta_1	`_easydiffraction_peak.decay_beta_1`	coreCIF
	rise_alpha_0	`_easydiffraction_peak.rise_alpha_0`	coreCIF
	rise_alpha_1	`_easydiffraction_peak.rise_alpha_1`	coreCIF

Total Scattering

pd-neut-total pd-xray-total

How to access in the codeKeys in EdiKeys in CIF

Category	Parameter	How to access in the code
peak	cutoff_q	peak.cutoff_q
	broad_q	peak.broad_q
	sharp_delta_1	peak.sharp_delta_1
	sharp_delta_2	peak.sharp_delta_2
	damp_q	peak.damp_q
	damp_particle_diameter	peak.damp_particle_diameter

Category	Parameter	Key in Edi
peak	cutoff_q	`_peak.cutoff_q`
	broad_q	`_peak.broad_q`
	sharp_delta_1	`_peak.sharp_delta_1`
	sharp_delta_2	`_peak.sharp_delta_2`
	damp_q	`_peak.damp_q`
	damp_particle_diameter	`_peak.damp_particle_diameter`

Category	Parameter	Key in CIF	CIF dictionary
peak	cutoff_q	`_easydiffraction_peak.cutoff_q`	coreCIF
	broad_q	`_easydiffraction_peak.broad_q`	coreCIF
	sharp_delta_1	`_easydiffraction_peak.sharp_delta_1`	coreCIF
	sharp_delta_2	`_easydiffraction_peak.sharp_delta_2`	coreCIF
	damp_q	`_easydiffraction_peak.damp_q`	coreCIF
	damp_particle_diameter	`_easydiffraction_peak.damp_particle_diameter`	coreCIF