4.1. Input files for Standard mode

An example of an input file for the standard mode is as follows:

W = 2
 L = 4
 model = "spin"
 method = "Lanczos"

 lattice = "triangular lattice"
//mu = 1.0
// t = -1.0
// t' = -0.5
// U = 8.0
//V = 4.0
//V'=2.0
J = -1.0
J'=-0.5
// nelec = 8
2Sz = 0

Basic rules for input files

• In each line, there is a set of a keyword (before an “=”) and a parameter(after an “=”); they are separated by “=”.

• You can describe keywords in a random order.

• Empty lines and lines beginning with a “//”(comment outs) are skipped.

• Upper- and lowercase are not distinguished. Double quotes and blanks are ignored.

• There are three types of parameters.

  1. Parameters that must be specified (if not, HPhi++ will stop with error messages),

  2. Parameters that it is not necessary to specified (if not specified, default values are used),

  3. Parameters that must not be specified (if specified, HPhi++ will stop with error messages).

  An example of type 3 is the transfer \(t\) parameter for the Heisenberg spin system. If you choose “model=spin”, you should not specify “\(t\)”.

We explain each keyword as follows.

• 4.1.1. Parameters for the type of calculation
• 4.1.2. Parameters for the lattice
• 4.1.3. Parameters for conserved quantities
• 4.1.4. Parameters for the Hamiltonian
• 4.1.5. Parameters for the numerical condition
• 4.1.6. Parameters for the dynamical Green’s function
• 4.1.7. Parameters for time-evolution