SSE program for the 2D S=1/2 Heisenberg antiferromagnet
Program: ssebasic
For given lattice lengths Lx, Ly, and inverse temperature beta=J/T, the program computes the energy, specific heat, squared sublattice magnetization, magnetic susceptibility.
Input:
File read.in containing:
lx ly beta nbin msteps isteps
Line 1 Column 1: System x length lx (integer)
Line 1 Column 2: System x length ly (integer)
Line 1 Column 3: Inverse temperature beta=J/T (real)
Line 2 Column 1: Number of bins (integer)
Line 2 Column 2: Number of MC sweeps / bin (integer)
Line 2 Column 3: Number of MC sweeps for equilibration (integer)
Example read.in (N=8)
8 8 4.0
20 100000 10000
File seed.in containing a random number seed
(integer)
Output:
Written to a file results.txt. This file is written after each completed bin. Self-explanatory contents, including the expansion cut-off L determined, the number of bins completed so far, and averages and error bars of the computed quantities.
With the read.in file given above, the following output was generated in results.txt (the results of course depend on the random seed used). Note the large error bar on the specific heat. It is very difficult to compute it accurately for large systems at low T.
Cut-off L : 486 Number of bins completed : 20 ========================================= -E/N : 0.66835206 0.00007645 C/N : 0.04917518 0.00565429 m**2 : 0.17669511 0.00011172 X(0,0) : 0.05462225 0.00006588 =========================================
This calculation took about 2.5 minutes on a MacBook Air.