MSallermann
commented
2 years ago Hi Sayan,
to define pairs acting within the unit cell set da=db=dc=0 and use the indices i and j.
See for example the little ascii picture below, where pair A acts between two different unit cells and therefore da=1. On the other hand, pair B acts within the same unit cell but with different indices within the unit cell. The index of the basis atoms depends on the order in which you specify their position in the input file.
A
┌──────────┐
│ │
┌┴─────┬────▼─┐
┌──┤0 1 │0 1 │
B │ │ │ │
└──►2 3 │2 3 │
└──────┴──────┘
i j da db dc
pair A: 0 1 1 0 0
pair B: 0 2 0 0 0
Sayan611
Dear SPIRIT developers, I have a question regarding the specification of translation integers (da db dc) in SPIRIT. Suppose I have a unit cell containing four atoms, and I have set up
################### Geometry #####################
Lattice constant for basis and translations
lattice_constant 1.0
The bravais lattice type
bravais_vectors 1.00 0.000000 0.0 0.00 0.707107 0.0 0.00 0.000000 1.0 basis 4 0.25 0.0000 0.0 0.50 0.5000 0.0 0.00 0.5000 0 0.75 0.0000 0.0
Number of basis cells along principal directions (a b c)
n_basis_cells 40 40 1 ################# End Geometry ###################
then in the case of heisenberg_pairs Hamiltonian how should I define "da db" to specify the interactions within the atoms inside the unit cell (as the values become fractional)? Below I have given the interaction of 0 th atom with the other 3 atoms inside one unit cell. i j da db dc Dijx Dijy Dijz Jij 0 1 0 0 0 -3.5e-03 2.8e-01 8.3e-02 17.5 0 2 0 0 0 -3.1e-02 1.4e-01 -7.7e-01 30.7 0 3 0 0 0 -1.6e-10 -8.9e-01 4.4e-11 -36.5 Is this correct? I will be grateful if you kindly help me in this matter. Thank you.
Regards Sayan Banik