4.2.12. Ising file

This file determines the values of Ising interactions \(J_{ij}^{z}\) (for \(S=1/2\) system). For the fermion electronic system, the Ising terms are given as

\[{\mathcal H}+=\sum_{i,j}J_{ij}^{z} (n_{i\uparrow}-n_{i\downarrow})(n_{j\uparrow}-n_{j\downarrow} ).\]

For the spin system, they are given as

\[{\mathcal H}+=\sum_{i,j}J_{ij}^{z} S_ {i}^{z}S_{j}^z.\]

An example of the file format is as follows.

======================
NIsing 6
======================
========Ising ======
======================
   0     1  0.50000
   1     2  0.50000
   2     3  0.50000
   3     4  0.50000
   4     5  0.50000
   5     0  0.50000

File format

  • Line 1: Header
  • Line 2: [string01] [int01]
  • Lines 3-5: Header
  • Lines 6-: [int02] [int03] [double01].

Parameters

  • [string01]

    Type : String (a blank parameter is not allowed)

    Description : A keyword for the total number of Ising interactions. You can freely give a name to the keyword.

  • [int01]

    Type : Int (a blank parameter is not allowed)

    Description : An integer giving the total number of Ising interactions.

  • [int02], [int03]

    Type : Int (a blank parameter is not allowed)

    Description : An integer giving a site index (\(0<=\) [int02], [int03] \(<\) Nsite).

  • [double01]

    Type : Double (a blank parameter is not allowed)

    Description : A value for \(J_{ij}^{\rm z}\).

Use rules

  • Headers cannot be omitted.
  • A program is terminated when the components of the Ising interactions are double counted.
  • A program is terminated when [int01] is different from the total number of Ising interactions defined in this file.
  • A program is terminated when either [int02] or [int03] is outside the range of the defined values.