ACEfriction.MatrixModels.CWCMatrixModel — Type
CWCMatrixModel(property, species_friction, species_env; maxorder=2, maxdeg=5, rcut=5.0, n_rep=1, ...)

Column-wise coupled friction model (onsite + spherical offsite).

Renamed from `RWCMatrixModel`

This model was formerly called RWCMatrixModel. The coupling scheme named row-wise coupling in Appendix C of the reference paper (Sachs et al., 2024) is more appropriately termed column-wise coupling, the terminology used here. Constructing RWCMatrixModel now raises an error pointing to CWCMatrixModel.

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CWCMatrixModel(property, species_friction, species_env, evalcenter::EvaluationCenter;
               rcut_on, rcut_off, maxorder_on, maxdeg_on, ..._on/_off, bond_weight)

Backward-compatible CWC constructor with a positional evalcenter and separate onsite/offsite hyperparameters (mirrors the pre-ET interface).

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ACEfriction.MatrixModels.PWCMatrixModel — Type
PWCMatrixModel(property, species_friction, species_env;
    maxorder=2, maxdeg=5, rcut=5.0, n_rep=1, ...)

Pairwise-coupled (offsite) friction model with a spherical pair environment.

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PWCMatrixModel(property, species_friction, species_env, cutoff::EllipsoidCutoff; ...)

Pairwise-coupled offsite model with an ellipsoidal (bond-centred) environment.

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PWCMatrixModel(property, species_friction, species_env, cutoff::SnowManCutoff; ...)

Pairwise-coupled offsite model with a symmetrised atom-centred environment: the block of pair (i,j) is c·basis(sphere_i, bond i→j) + c·basis(sphere_j, bond j→i) (two overlapping spheres, one per bond end). cutoff.rcut is the per-centre radius. Accepts the same selection/radial keywords as the other PWCMatrixModel methods.

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The first argument of every constructor is an equivariant block property (Invariant, EuclideanVector, EuclideanMatrix, or SymmetricEuclideanMatrix) fixing the $O(3)$ transformation law of the blocks ${\bm \Sigma}_{ij}$; see Equivariant block properties. The block sparsity and assembly of ${\bm \Sigma}$ (the coupling scheme) are summarised in Matrix models and coupling schemes.

Local environments (cutoffs)

The local environment entering each block is delimited by one of the following cutoffs (see also Local environments (cutoffs)):

ACEfriction.ETBackend.SphericalCutoff — Type
SphericalCutoff(rcut)

Spherical pair-environment cutoff for the atom-centred offsite model: the bond environment of a pair (i,j) is the set of neighbours of atom i within rcut, with j itself the bond partner. (Cf. ACEfrictionCore SphericalCutoff.)

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ACEfriction.ETBackend.EllipsoidCutoff — Type
EllipsoidCutoff(rcutbond, rcutenv, zcutenv)

Bond-centred ellipsoidal cutoff: bonds with |rij| <= rcutbond; environment atoms within the ellipsoid (z/zcutenv)^2 + (r/rcutenv)^2 <= 1 around the bond midpoint (z along the bond, r perpendicular).

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ACEfriction.ETBackend.SnowManCutoff — Type
SnowManCutoff(rcut, symmetry = :symmetric)

Atom-centred pair-environment cutoff combining both bond ends: the diffusion block of a pair (i,j) evaluates the ACE basis on the spherical environment of i (with j the bond partner) and on the spherical environment of j (with i the bond partner) — two overlapping spheres, one per bond end (the "snowman") — and combines them with the same coefficients. The combination is selected by symmetry:

:symmetric      Σ_ij = c · basis(sphere_i, bond i→j) + c · basis(sphere_j, bond j→i)
:antisymmetric  Σ_ij = c · basis(sphere_i, bond i→j) - c · basis(sphere_j, bond j→i)

symmetry is carried as a (Symbol-valued) type parameter SnowManCutoff{T, S} so the assembly dispatches on it. rcut is the per-centre spherical radius (same convention as SphericalCutoff).

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