def get_mps(K,Jp,J1=1.,J2=0.2412,nsite=30,which='finite',data_file=None):
'''
Run finite-DMFT/lanczos for two impurity Kondo model to get the Ground state energy.
Parameters:
:J1/J2/K/Jp: float, the parameters defining the model.
:nsite: integer, the number of sites, must be even.
:which: 'finite'/'lanczos', select the method to solve the chain, 'finite dmrg' or 'lanczos'.
'''
assert(which=='finite' or which=='lanczos')
assert(nsite%2==0)
model=TIKM(J1=J1,J2=J2,K=K,Jp=Jp,nsite=nsite)
hgen=SpinHGen(spaceconfig=model.spaceconfig,evolutor=MaskedEvolutor(hndim=model.spaceconfig.hndim) if which=='finite' else NullEvolutor(hndim=2))
dmrgegn=DMRGEngine(hchain=model.H_serial,hgen=hgen,tol=0)
if which=='lanczos':
H=get_H(H=model.H_serial,hgen=hgen)
EG,EV=eigsh(H,k=1)
mps=state2MPS(EV[:,0])
else:
EG=dmrgegn.run_finite(endpoint=(2,'<-',0),maxN=[10,20],tol=0)[-1]
mps=dmrgegn.get_mps(direction='<-') #right normalized initial state
if data_file is not None:
mps.save(data_file)
return mps
def heisenberg_vmps(J,Jz,h,nsite,append=False):
'''
Run vMPS for Heisenberg model.
'''
filename='mps_heisenberg_%s.dat'%(nsite)
model=HeisenbergModel(J=J,Jz=Jz,h=h,nsite=nsite)
if append:
mps=MPS.load(filename)
else:
#run dmrg to get the initial guess.
hgen=RGHGen(spaceconfig=model.spaceconfig,H=model.H_serial,evolutor_type='masked')
dmrgegn=DMRGEngine(hgen=hgen,tol=0)
EG=dmrgegn.run_finite(endpoint=(1,'<-',0),maxN=10,tol=0)[-1]
#hgen=dmrgegn.query('r',nsite-1)
mps=dmrgegn.get_mps(direction='<-') #right normalized initial state
mps.save(filename)
#run vmps
vegn=VMPSEngine(H=model.H,k0=mps)
vegn.run()
def test_vmps(self):
'''
Run vMPS for Heisenberg model.
'''
nsite=10
filename='mps_heisenberg_%s.dat'%(nsite)
model=self.get_model(nsite,which=1)
#mps=MPS.load(filename)
#run dmrg to get the initial guess.
hgen=SpinHGen(spaceconfig=SpinSpaceConfig([2,1]),evolutor=MaskedEvolutor(hndim=2))
dmrgegn=DMRGEngine(hchain=model.H_serial,hgen=hgen,tol=0)
dmrgegn.run_finite(endpoint=(1,'<-',0),maxN=40,tol=1e-12)
#hgen=dmrgegn.query('r',nsite-1)
mps=dmrgegn.get_mps() #right normalized initial state
mps.save(filename)
#run vmps
vegn=VMPSEngine(H=model.H,k0=mps)
vegn.run()
def spin1_vmps(J, Jz, h, nsite, append=False):
"""
Run vMPS for Heisenberg model.
"""
filename = "mps_heisenberg_%s.dat" % (nsite)
model = Spin1Model(J=J, Jz=Jz, h=h, nsite=nsite)
if append:
mps = MPS.load(filename)
else:
# run dmrg to get the initial guess.
hgen = RGHGen(spaceconfig=SpinSpaceConfig([2, 1]), H=model.H_serial, evolutor_type="masked")
dmrgegn = DMRGEngine(hgen=hgen, tol=0)
EG = dmrgegn.run_finite(endpoint=(1, "<-", 0), maxN=10, tol=0)[-1]
# hgen=dmrgegn.query('r',nsite-1)
mps = dmrgegn.get_mps(direction="<-") # right normalized initial state
mps.save(filename)
# run vmps
vegn = VMPSEngine(H=model.H, k0=mps)
vegn.run()
