Short tutorial
Once you have your lattice file generated you need an initial state with mp-random
to start the ground state calculation:
mp-random -l lattice -o gs-init
In case you are using symmetries you need to specify them via e.g. -q 30,0
(N=30, Sz=0).
Note that on 2007-08-16, a bug was found in mp-random. It accidentally always took the 4th parameter as the output filename, rather than the -o
option. The above line accidentally works, because 'gs-init' happens to be the 4th parameter. It wouldn't work properly if you tried mp-random -l lattice -q 30,0 -o gs-init
. (It would write the wave function to the file named '30,0') This is now fixed.
-> Ian
Now we set up the dmrg calculation and then run it.
mp-dmrg-init -H lattice:H -w gs-init -c dmrg.conf -o gs
mp-dmrg-resume gs
The result is a file called gs.psi.##
, ##
being the number of sweeps performed, which holds the calculated ground state.
With that state you can calculate all sorts of expectation values using mp-[local]expectation[2]
and correlations using mp-localcorrelation
which should be preferred over mp-correlation
Note on SU(2) symmetric models
- When creating the Hamiltonian nearest neighbour hopping terms need an additional factor of sqrt(2) compared to an U(1) model.
- One needs to multiply all
S*S
correlations with -sqrt(3)!