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()