(swsym-bond)=

# swsym.bond

## Syntax
  
`[genBond, uBond] = swsym.bond(r,bv,bond,symOp)`
  
`[genBond, uBond] = swsym.bond(r,bv,bond,symOp,tol)`
 
## Description
  
`[genBond, uBond] = swsym.bond(r,bv,bond,symOp)` generates all bonds that
are symmetry equivalent to the given `bond`. The function uses the given
space group operators and positions of magnetic atoms to return a list of
equivalent bonds in a matrix. The function also checks the validity of
the calculation by measuring the length of each equivalent bond using the
given `bv` base and if the difference in length between equivalent bonds
is larger than the tolerance throws a warning.
  
`[genBond, uBond] = swsym.bond(r,bv,bond,symOp,tol)` also defines the
tolerance using `tol`.
 
## Input Arguments
  
`r`
: Positions of the magnetic atoms in lattice units stored in a matrix
  with dimensions of $[3\times n_{magAtom}]$.
  
`bv`
: Basis vectors that define the lattice, used for checking the bond
  length of equivalent bonds, see [spinw.basisvector](#spinw-basisvector) for details.
  
`bond`
: Vector that contains the starting bond with elements of 
  `[dl_a dl_b dl_c atom_1 atom_2]`, where `dl` is vector of lattice
  translation between the two atoms if they are not in the same unit cell
  in lattice units, `atom_1` and `atom_2` are indices of atoms in the
  list of positions stored in `r`.
  
`symOp`
: Matrix, that contains the rotation and translation operators of
  the space group with dimensions of $[3\times 4\times n_{op}]$.
  
`tol`
: Tolerance, default value is $10^{-5}$.
  
## Output Arguments
  
`genBond`
: Matrix, whith each column defines a bond, the meaning of each
          row is the same as the input `bond` variable.
 
`uBond`
: Logical variable, `true` if all the generated bonds are unique.
  
## See Also
  
[spinw.gencoupling](#spinw-gencoupling) \| [swsym.operator](#swsym-operator) \| [swsym.position](#swsym-position)