Version History

v0.7.3

(In development)

Fix error in print_symmetry_table for slightly-distorted crystal cells (PR #317).

v0.7.2

(Sep 11, 2024)

Fix error in SampledCorrelations with a coarse $𝐪$-grid. (PR #314).
Fix colorbar in plot_intensities! when all data is uniform (PR #315).
An explicit colorrange can be used for plotting intensities_bands.

v0.7.1

(Sep 3, 2024)

Correctness fix for scalar biquadratic interactions specified with option biquad to set_exchange!.
Prototype implementation of entangled units.

v0.7.0

(Aug 30, 2024)

This major release introduces breaking interface changes.

The interface for calculating intensities has been revised to unify functionality across backends. The functions intensities_bands, intensities, and intensities_static no longer expect a "formula", and instead take keyword arguments directly. Pair correlations are now specified using ssf_perp and related functions. The constructors SampledCorrelations and SampledCorrelationsStatic replace dynamic_correlations and static_correlations, respectively.
New function plot_intensities enables convenient plotting for many types of intensities plots. Mutating variant plot_intensities! enables multi-panel plots.
One should now specify a range of $𝐪$-points with q_space_path or q_space_grid.
SpinWaveTheorySpiral is available to perform calculations on generalized spiral structures, which may be incommensurate.
repeat_periodically_as_spiral replaces set_spiral_order_on_sublattice! and set_spiral_order!.
New convenience functions powder_average and domain_average, which wrap intensities.
System now expects supercell dimensions as a dims keyword argument. Moment replaces SpinInfo. Lower-case s now labels quantum spin. For example, use :dipole_large_s instead of :dipole_large_S.
In view_crystal and plot_spins use ndims instead of dims for the number of spatial dimensions.
Binning features have been removed. Some functionality may be added back in a future release.
Experimental SpinWaveTheoryKPM feature implements a new algorithm to enable intensities calculations at a computational cost that scales linearly in system size.

v0.6.1

(Aug 2, 2024)

Breaking changes: magnetic_moment is now reported in units of the Bohr magneton, $μ_B$. For model systems where the Zeeman coupling aligns spin dipole with field (e.g., the Ising model convention), create a SpinInfo with g=-1. (PR 284).
More flexible Units system. set_external_field! is deprecated in favor of set_field!, which now expects a field in energy units. enable_dipole_dipole! now expects a scale parameter $μ_0 μ_B^2$ that can be obtained from units.vacuum_permeability.

v0.6.0

(Jun 18, 2024)

Various correctness fixes. The magnetic moment is now anti-aligned with the spin dipole (Issue 190), and the wavevector $𝐪$ in structure factor intensities $\mathcal{S}(𝐪,ω)$ now consistently represents momentum transfer to the sample (Issue 270). The new Example 8 demonstrates a model system where momentum transfers $±𝐪$ are inequivalent.
Dynamical structure factor intensities now have a precisely defined scale, independent of the calculator (Issue 264). Consequently, color ranges in plots may need to be rescaled.
Crystal can now infer a chemical unit cell from an mCIF file. System now supports set_dipoles_from_mcif!. Through spglib, one can now standardize any Crystal, with an option to idealize site positions.

v0.5.10

(May 27, 2024)

view_crystal called on a System now shows interactions, and optionally the spin or magnetic dipoles.
Interactions for enable_dipole_dipole! are now supported in linear spin wave theory, with proper Ewald summation. For a faster alternative, the experimental function modify_exchange_with_truncated_dipole_dipole! will accept a real-space cutoff.
Intensities calculated with dynamic_correlations now avoid "bleeding artifacts" at low-energy (long-timescale) modes. See PR 246 for details. This eliminates the need for process_trajectory=:symmetrize.
When passed to intensity_formula, the special value zero(FormFactor) can now be used to disable contributions from a given site. For an example, see the ported SpinW tutorial 19.
Broadening kernels gaussian and lorentzian now expect a full width at half maximum (fwhm) keyword argument.
Experimental support for calculations on generalized spiral phases. For an example, see the ported SpinW tutorial 18.
Correctness fix for the case where spin-$S$ varies between sites in dipole-mode. In SU($N$) mode, however, there is still no support for varying the Hilbert space dimension $N$ between sites.
Correctness fix in long-range dipole-dipole interactions for systems with multiple cells.
Correctness fix in general biquadratic interactions (beyond scalar) for spin wave theory in dipole-mode.
Correctness fix for reading Mantid .nxs files.

v0.5.9

(Mar 25, 2024)

Correctness fixes: Structure factor conventions are now uniform across modes and precisely specified. The g-tensor is applied by default (disable with apply_g = false). The intensity is additive with increasing number of magnetic ions in the chemical cell, consistent with SpinW. Issue #235.
Enhancements to view_crystal. If a bond allows a DM interaction, its orientation will be shown visually. If a System argument is supplied, its exchange interactions will be shown..
New function suggest_timestep to assist in performing accurate and efficient simulation of classical spin dynamics. Issue #149.
Scalar biquadratic interactions can again be set in :dipole_large_S mode via the keyword argument biquad of set_exchange!.
Significantly speed up dynamic_correlations for crystals with many atoms in the unit cell. Issue #204.
Renamings: dt replaces Δt and damping replaces λ. This affects Langevin, [ImplicitMidpoint], and dynamic_correlations functions.

v0.5.8

(Jan 4, 2024)

Many bugs in the WGLMakie backend have become apparent, and are being tracked at Issue #211. Emit a warning if WGLMakie is detected, suggesting that GLMakie is preferred.
Various improvements to view_crystal. A distance parameter is no longer expected. Cartesian axes now appear as "compass" in bottom-left. Custom list of reference bonds can be passed. Toggle to view non-magnetic atoms in root crystal. Atoms now colored using CPK/JMol conventions.

v0.5.7

(Nov 26, 2023)

Update form factor coefficients, which now include Mn5.
Fix merge_correlations and the Parallelizing Calculations tutorial.
Remove internal functions *_primitive_crystal. Instead, it is recommended to use the conventional unit cell, and later call reshape_supercell.
Require Makie 0.20. An important new feature is resolution-independent scaling of font sizes. New figures expect size instead of resolution, and no longer accept rescale.

This release initiates some major enhancements to the user interface in support of generalized SU(N) spin models. See this documentation page for an illustration of the new features. Most existing Sunny 0.5 models will continue to work with deprecation warnings, but these will become hard errors Sunny v0.6.

General pair couplings are now supported in set_pair_coupling! and set_pair_coupling_at!. :SUN mode supports interactions of any order, but :dipole mode is limited to bilinear and biquadratic coupling of the spin.
To perform a calculation with dipoles in the large-$S$ limit, use the new mode :dipole_large_S when constructing a System.
Deprecate the option biquad to set_exchange!. Use instead set_pair_coupling!, which generalizes beyond the scalar biquadratic.
Deprecate spin_operators, stevens_operators, large_S_spin_operators and large_S_stevens_operators. Use instead spin_matrices and stevens_matrices, which require a specific spin-$S$ label. To infer this, one can use spin_label.
Remove unused option energy_tol in SpinWaveTheory.
Animated spin dynamics is now possible. Call notify on the result of plot_spins to trigger redrawing of the frame. The argument colorfn to plot_spins supports animation of colors. See example usage for a Heisenberg ferromagnetic.
Add set_spin_rescaling! feature, which supports improved spectral measurements at finite-$T$. This follows the method proposed in Dahlbom et al., [arXiv:2310.19905].

v0.5.5

(Sep 29, 2023)

reshape_supercell now allows reshaping to multiples of the primitive unit cell, which can speed up certain calculations. This is illustrated in the CoRh₂O₄ powder averaging tutorial.
resize_supercell now allows all resizings.
Added energy_per_site.
set_spiral_order_on_sublattice! cannot work on reshaped systems.
Various bug fixes. In particular, an intensity_formula with :full will now uniformly calculate a 3x3 matrix of complex numbers.

v0.5.4

(Sep 11, 2023)

Various enhancements to view_crystal. Atoms are now labeled by index, and bonds support interactive inspection (GLMakie only). Font sizes work correctly on Makie v0.20-beta. If using Makie v0.19 on a high-resolution display, pass rescale=1.5 to enlarge font sizes.
The function suggest_magnetic_supercell now requires only a list of wavevectors, and will return a $3×3$ matrix that can be programmatically passed to reshape_supercell. The new tolerance parameter tol allows suggest_magnetic_supercell to approximate incommensurate wavevectors with nearby commensurate ones.
New functions set_spiral_order! and set_spiral_order_on_sublattice! can be used to initialize a spiral, single-$Q$ order.
Sunny now retains all constant energy shifts that have been introduced by anisotropy operators.
Fix export_vtk functionality.

v0.5.3

(Sep 8, 2023)

Add large_S_spin_operators and large_S_stevens_operators to support single-ion anisotropies in dipole mode without renormalization. Set large_S=true in set_exchange! to avoid renormalization of biquadratics.
view_crystal has been rewritten in Makie.
plot_spins now expects ghost_radius in physical length units.
SpinWaveTheory will (currently) error if provided a system with enable_dipole_dipole!.

v0.5.2

(Aug 30, 2023)

Form factors for 5d transition ions.
Download links for notebooks and scripts on each doc example
Various bug fixes.

v0.5.1

(Aug 23, 2023)

Fix binning edge cases.
plot_spins accepts resolution argument.

v0.5.0

(Aug 21, 2023)

New features.

Support for Linear Spin Wave Theory in :dipole and :SUN modes. (Thanks Hao Zhang!)

New function minimize_energy! to efficiently find an optimal configuration of spin dipoles or SU(N) coherent states.

Major refactors and enhancements to intensity calculations. This new interface allows unification between LSWT and classical spin dynamics calculations. This interface allows: Custom observables as local quantum operators, better support for linebroadening, and automatic binning to facilitate comparison with experimental data. See intensity_formula for documentation. Use load_nxs to load experimental neutron scattering data.

Breaking changes.

Require Julia 1.9.

Replace set_anisotropy! with a new function set_onsite_coupling! (and similarly set_onsite_coupling_at!). The latter expects an explicit matrix representation for the local Hamiltonian. This can be constructed, e.g., as a linear combination of stevens_operators, or as a polynomial of spin_operators. To understand the mapping between these two, the new function print_stevens_expansion acts on an arbitrary local operator.

Remove set_biquadratic!. Instead, use an optional keyword argument biquad to set_exchange!.

Rename DynamicStructureFactor to dynamic_correlations. Similarly, replace InstantStructureFactor with instant_correlations. The return type has been renamed SampledCorrelations to emphasize that the object may be holding thermodynamic samples, which are collected using add_sample!. Upon construction, the SampledCorrelations object will be empty (no initial sample).

Remove intensities function. Instead, use one of intensities_interpolated or intensities_binned. These will require an intensity_formula, which defines a calculator (e.g., LSWT).

Rename connected_path to reciprocal_space_path, which now returns an xticks object that can be used in plotting. Replace spherical_shell with reciprocal_space_shell that functions similarly.

Rename polarize_spin! to set_dipole! for consistency with set_coherent!. The behavior of the former function is unchanged: the spin at a given site will still be polarized along the provided direction.

Rename all_sites to eachsite consistent with Julia convention for iterators.

Rename reshape_geometry to reshape_supercell, which is the fundamental reshaping function. Rename resize_periodically to resize_supercell.

The constructor SpinInfo now requires a $g$-factor or tensor as a named argument.

The constructor FormFactor no longer accepts an atom index. Instead, the form factors are associated with site-symmetry classes in order of appearance.

v0.4.3

(Jun 23, 2023)

Experimental support for linear SpinWaveTheory, implemented in SU(N) mode. This module may evolve rapidly.

Implement renormalization of single-ion anisotropy and biquadratic interactions when in :dipole mode. This makes the model more faithful to the quantum mechanical Hamiltonian, but is also a breaking change.

Various improvements and bugfixes for to_inhomogeneous. Setting inhomogeneous interactions via set_exchange_at! should now infer the correct bond offset direction, or will report an ambiguity error. Ambiguities can be resolved by passing an explicit offset.

The function remove_periodicity! disables periodicity along specified dimensions.

Rename StaticStructureFactor to InstantStructureFactor.

v0.4.2

(Feb 27, 2023)

Introduce LocalSampler, a framework for MCMC sampling with local spin updates.

Rename print_dominant_wavevectors to print_wrapped_intensities to reduce confusion with the physical instantaneous intensities.

The function spherical_shell now takes a radius in physical units of inverse Å.

New exported functions global_position, magnetic_moment, all_sites.

Remove all uses of Base.deepcopy which resolves crashes.

v0.4.1

(Feb 13, 2023)

The function to_inhomogeneous creates a system that supports inhomogeneous interactions, which can be set using set_exchange_at!, etc.

set_biquadratic! replaces set_exchange_with_biquadratic!.

v0.4.0

(Feb 10, 2023)

This update includes many breaking changes, and is missing some features of 0.3.0.

Creating a spin `System`

Rename SpinSystem to System. Its constructor now has the form,

System(crystal, dims, infos, mode)

The parameter infos is now a list of SpinInfo objects. Each defines spin angular momentum $S = \frac{1}{2}, 1, \frac{3}{2}, …$, and an optional $g$-factor or tensor.

The parameter mode is one of :SUN or :dipole.

Setting interactions

Interactions are now added mutably to an existing System using the following functions: set_external_field!, set_exchange!, set_onsite_coupling!, enable_dipole_dipole!.

As a convenience, one can use dmvec(D) to convert a DM vector to a $3×3$ antisymmetric exchange matrix.

Fully general single-ion anisotropy is now possible. The function set_onsite_coupling! expects the single ion anisotropy to be expressed as a polynomial in symbolic spin operators 𝒮, or as a linear combination of symbolic Stevens operators 𝒪. For example, an easy axis anisotropy in the direction n may be written D*(𝒮⋅n)^2.

Stevens operators 𝒪[k,q] admit polynomial expression in spin operators 𝒮[α]. Conversely, a polynomial of spin operators can be expressed as a linear combination of Stevens operators. To see this expansion use print_anisotropy_as_stevens.

Inhomogeneous field

An external field can be applied to a single site with set_external_field_at!.

Structure factor rewrite

The calculation of structure factors has been completely rewritten. For the new interface see the documentation tutorials.

Various

The "Sampler" interface is in flux. Langevin replaces both LangevinHeunP and LangevinSampler. Local spin-flip Monte Carlo sampling methods are temporarily broken.
repeat_periodically replaces extend_periodically.

Additional related functions include resize_periodically and reshape_geometry, the latter being fundamental.

print_symmetry_table replaces print_bond_table().

The new function includes the list of symmetry-allowed single ion anisotropies in addition to exchange interactions.

When reading CIF files, the field _atom_site_label is now used in place of the field _atom_site_type_symbol.

This is required for correctness. The field _atom_site_label is guaranteed to be present, and is guaranteed to be a distinct label for each symmetry-inequivalent site. Code that explicitly referred to site labels (e.g. in calls to subcrystal) will need to be updated to use the new label.