Coordinate systems
SpinW uses four coordinate systems.
Contents
abc coordinate system
This is the lattice coordinate system, every vector, whose components are given in lattice units are in this coordinate system. The three axis are the a, b and c crystal axes. The axis length can be normalized to one or to the lattice parameters. The following [[SwclassEN][sw class]] properties are stored in lattice units:
- atomic positions ([[SwpropertiesEN#2][sw.unit_cell]].r)
- translation vectors for bonds ([[SwpropertiesEN#6][sw.coupling]].dl)
Also several function takes input or aoutput in lattice units:
- atomic positions of the output of sw.matom and sw.atom methods (sw.matom.r, sw.atom.r)
- magnetic moments can be given in lattice units for the sw.genmagstr method (using the 'unitS' option with 'lu' value)
- calculated bond vector by sw.couplingtable
xyz coordinate system
Most of the [[SwclassEN][sw class]] properties are stored in the xyz coordinate system. The xyz coordinate system is right-handed Cartesian and fixed to the crystal lattice:
- x: parallel to a-axis,
- y: perpendicular to x and in the ab-plane,
- z: perpendicular to xy-plane
The following properties are in xyz coordinate system:
- twin rotation matrices ([[SwpropertiesEN#3][sw.twin]].rotc)
- stored 3x3 matrices ([[SwpropertiesEN#4][sw.matrix]].mat)
- magnetic field ([[SwpropertiesEN#5][sw.single_ion]].field)
- magnetic moment components ([[SwpropertiesEN#7][sw.mag_str]].S)
- normal vector of the magnetic structure ([[SwpropertiesEN#7][sw.mag_str]].n)
Also output of different functions are in xyz coordinate system:
- spin-spin correlation function calculated by sw.spinwave method (spec.Sab matrices)
- interaction matrices calculated by sw.couplingtable
reciprocal lattice coordinate system
The reciprocal lattice coordinate system is the dual vector space of the lattice coordinate system. The three axis are the reciprocal lattice vectors denoted by a*, b* and c* LATEXf(x,y)=x^2+y^2PATEX.