Hamiltonian

#include "Spirit/Hamiltonian.h"

This currently only provides an interface to the Heisenberg Hamiltonian.

DMI chirality

This means that

Bloch chirality corresponds to DM vectors along bonds
Neel chirality corresponds to DM vectors orthogonal to bonds

Neel chirality should therefore only be used in 2D systems.

SPIRIT_CHIRALITY_BLOCH

SPIRIT_CHIRALITY_BLOCH 1

Bloch chirality

SPIRIT_CHIRALITY_NEEL

SPIRIT_CHIRALITY_NEEL  2

Neel chirality

SPIRIT_CHIRALITY_BLOCH_INVERSE

SPIRIT_CHIRALITY_BLOCH_INVERSE -1

Bloch chirality, inverted DM vectors

SPIRIT_CHIRALITY_NEEL_INVERSE

SPIRIT_CHIRALITY_NEEL_INVERSE  -2

Neel chirality, inverted DM vectors

Dipole-Dipole method

SPIRIT_DDI_METHOD_NONE

SPIRIT_DDI_METHOD_NONE   0

Do not use dipolar interactions

SPIRIT_DDI_METHOD_FFT

SPIRIT_DDI_METHOD_FFT    1

Use fast Fourier transform (FFT) convolutions

SPIRIT_DDI_METHOD_FMM

SPIRIT_DDI_METHOD_FMM    2

Use the fast multipole method (FMM)

SPIRIT_DDI_METHOD_CUTOFF

SPIRIT_DDI_METHOD_CUTOFF 3

Use a direct summation with a cutoff radius

Setters

Hamiltonian_Set_Boundary_Conditions

void Hamiltonian_Set_Boundary_Conditions(State *state, const bool* periodical, int idx_image=-1, int idx_chain=-1)

Set the boundary conditions along the translation directions [a, b, c]

Hamiltonian_Set_Field

void Hamiltonian_Set_Field(State *state, float magnitude, const float* normal, int idx_image=-1, int idx_chain=-1)

Set the (homogeneous) external magnetic field [T]

Hamiltonian_Set_Anisotropy

void Hamiltonian_Set_Anisotropy(State *state, float magnitude, const float* normal, int idx_image=-1, int idx_chain=-1)

Set a global uniaxial anisotropy [meV]

Hamiltonian_Set_Biaxial_Anisotropy

void Hamiltonian_Set_Biaxial_Anisotropy(
    State * state, const scalar * magnitude, const unsigned int exponents[][3], const scalar * primary,
    const scalar * secondary, int n_terms, int idx_image=-1, int idx_chain=-1)

Set a global biaxial anisotropy [meV] Note: the secondary axis will be orthogonalized with respect to the primary axis and both axes will be normalized.

Hamiltonian_Set_Exchange

void Hamiltonian_Set_Exchange(State *state, int n_shells, const float* jij, int idx_image=-1, int idx_chain=-1)

Set the exchange interaction in terms of neighbour shells [meV]

Hamiltonian_Set_DMI

void Hamiltonian_Set_DMI(State *state, int n_shells, const float * dij, int chirality=SPIRIT_CHIRALITY_BLOCH, int idx_image=-1, int idx_chain=-1)

Set the Dzyaloshinskii-Moriya interaction in terms of neighbour shells [meV]

Hamiltonian_Set_DDI

void Hamiltonian_Set_DDI(State *state, int ddi_method, int n_periodic_images[3], float cutoff_radius=0, bool pb_zero_padding=true, int idx_image=-1, int idx_chain=-1)

Configure the dipole-dipole interaction

ddi_method: see integers defined above
n_periodic_images: how many repetition of the spin configuration to append along the translation directions [a, b, c], if periodical boundary conditions are used
cutoff_radius: the distance at which to stop the direct summation, if used
pb_zero_padding: if True zero padding is used even for periodical directions

Getters

Hamiltonian_Get_Name

const char * Hamiltonian_Get_Name(State * state, int idx_image=-1, int idx_chain=-1)

Returns a string containing the name of the Hamiltonian in use

Hamiltonian_Get_Boundary_Conditions

void Hamiltonian_Get_Boundary_Conditions(State *state, bool * periodical, int idx_image=-1, int idx_chain=-1)

Retrieves the boundary conditions

Hamiltonian_Get_Field

void Hamiltonian_Get_Field(State *state, float * magnitude, float * normal, int idx_image=-1, int idx_chain=-1)

Retrieves the external magnetic field [T]

Hamiltonian_Get_Anisotropy

void Hamiltonian_Get_Anisotropy(State *state, float * magnitude, float * normal, int idx_image=-1, int idx_chain=-1)

Retrieves the uniaxial anisotropy [meV]

Hamiltonian_Get_Biaxial_Anisotropy_N_Atoms

int Hamiltonian_Get_Biaxial_Anisotropy_N_Atoms( State * state, int idx_image = -1, int idx_chain = -1 )

Retrieve the number of atoms within the unit cell for which a biaxial anisotropy is defined

Hamiltonian_Get_Biaxial_Anisotropy_N_Terms

void Hamiltonian_Get_Biaxial_Anisotropy_N_Terms(State * state, int idx_image = -1, int idx_chain = -1 )

Retrieve the total number of terms that define the biaxial anisotropy.

Hamiltonian_Get_Biaxial_Anisotropy

void Hamiltonian_Get_Biaxial_Anisotropy(
    State * state, int * indices, scalar primary[][3], scalar secondary[][3], int * site_p, const int n_indices,
    scalar * magnitude, int exponents[][3], const int n_terms, int idx_image = -1, int idx_chain = -1 )

Retrieve the data representing the biaxial anisotropy. Each index indices[i] has a corresponding primary[i] and secondary[i] axis as well as a range of terms [site_p[i], site_p[i+1]). The full list of terms is written to the magnitude (given in [meV]) and the exponents array respectively.

Hamiltonian_Get_Exchange_Shells

void Hamiltonian_Get_Exchange_Shells(State *state, int * n_shells, float * jij, int idx_image=-1, int idx_chain=-1)

Retrieves the exchange interaction in terms of neighbour shells.

Note: if the interactions were specified as pairs, this function will retrieve n_shells=0.

Hamiltonian_Get_Exchange_N_Pairs

int  Hamiltonian_Get_Exchange_N_Pairs(State *state, int idx_image=-1, int idx_chain=-1)

Returns the number of exchange interaction pairs

Hamiltonian_Get_DMI_Shells

void Hamiltonian_Get_DMI_Shells(State *state, int * n_shells, float * dij, int * chirality, int idx_image=-1, int idx_chain=-1)

Retrieves the Dzyaloshinskii-Moriya interaction in terms of neighbour shells.

Note: if the interactions were specified as pairs, this function will retrieve n_shells=0.

Hamiltonian_Get_DMI_N_Pairs

int  Hamiltonian_Get_DMI_N_Pairs(State *state, int idx_image=-1, int idx_chain=-1)

Returns the number of Dzyaloshinskii-Moriya interaction pairs

Hamiltonian_Get_DDI

void Hamiltonian_Get_DDI(State *state, int * ddi_method, int n_periodic_images[3], float * cutoff_radius,  bool * pb_zero_padding, int idx_image=-1, int idx_chain=-1)

Retrieves the dipole-dipole interaction configuration.

ddi_method: see integers defined above
n_periodic_images: how many repetitions of the spin configuration to append along the translation directions [a, b, c], if periodical boundary conditions are used
cutoff_radius: the distance at which to stop the direct summation, if method_cutoff is used
pb_zero_padding: if True zero padding is used even for periodical directions