June 2017 - Comp-phys-alps-users

measuring truncation errors in mps_optim
by Robertson Esperanza 07 Dec '17

07 Dec '17

Thank you for all the help so far, now I'm trying to check for convergence of my results. First, is it enough to just check how the truncation error changes with sweeps (at a certain MAXSTATE value) or I need to both check the iteration history of the ground state energy and the truncation error? Second, checking the supplementary materials provided (Computer Physics Communications 185 (2014) 3430–3440) for the Hubbard ladder, why are there 381 values of energy and truncation weights for every iteration? Why is the total truncation error for that iteration is the sum of all the 381 truncation weight values (based on iteration.py)? How is truncation error defined (e.g. is it 1 - sum of all reduced density eigenvalues corresponding to all the picked states?) ? As far as I understand the DMRG algorithm every iteration/sweep has a corresponding bond dimension in which as you progress through iterations (until you reach the "SWEEPS"th iteration), bond dimension increases until you reach "MAXSTATES" at the "SWEEPS"th iteration. Regards, Robertson Esperanza

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Long Range Kitaev Model site dependent Hamiltonian
by John Ian Kenneth E. Felismino 05 Jul '17

05 Jul '17

Hi! The hamiltonian I'm using is attached as a picture file. As you can see, the bond terms are proportional to abs(i - j)^\alpha. i was wondering if this is possible in Alps because I have tried doing it (crudely) with DMRG and found that it did not produce an output xml. I had simply added the term "/abs(i-j)^alpha#" in my hamiltonian. When I remove this term, the Hamiltonian works, so clearly the problem is with this proportionality term. Thanks. Ian Felismino

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Is entropy measurement available in MPS_OPTIM of ALPS Prerelease 2.3.0?
by Desmond 28 Jun '17

28 Jun '17

Hi Everyone, >From previous discussions and the documentations, I know that there is a hidden function in MPS_OPTIM that can measure the von Neumann entropy and n=2 Renyi entropy. I am wondering if this function is working in the binary code of ALPS Prerelease 2.3.0. When I include "'MEASURE[Entropy]' :1," in my input file, I see at the final stage of the calculation, there is a message "calculating vN entropy" on display. However, I could not find any result related to the vN entropy in the output file. I am wondering if I did something wrong or I need to compile a newer version that is not available in binary code. Thank you in advance! Desmond

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structure factor of lattice containing multi-sites in one unit cell
by 郭怀明 13 Jun '17

13 Jun '17

Dear all, Recently I use SSE QMC to perform a calculation of Bose-Hubbard model. The lattice I consider is basically a square lattice, but I use a plaquette containing four sites as a unit cell. I want to use structure factor to characterize possible CDW charge order. On normal square lattice, the momentum (\pi,\pi) can be chosen. However for the unit cell I chosen,how can I characterize the same CDW order? A similar case is Bose-Hubbard model on honeycomb lattice, what momentum is chosen for characterizing a CDW with staggered occupying the two inequivalent sites? Thank you very much! Sincerely, Huaiming Guo

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Conversion of Temperature to Kelvin
by Bheema Lingam Chittari 05 Jun '17

05 Jun '17

Dear Users, What is the conversion to the temperature in the plots to Kelvin units. What I understood is, the T units in the plots are in energy units (meV), to convert that to Kelvin units is just to divide the T values in meV by 0.0861 meV/K (1/k_B value in meV/K). Is this correct way? is there any method to do it? Is there any available method to plot Temperature in Kelvin units after the calculations within Python without any post processing. Thank you Dr. Bheema Lingam Chittari Post Doctoral Researcher, Room No:14-115, Department of Physics, University of Seoul, 163 Seoulsiripdae-ro, Dongdumen-gu, Seoul, South Korea

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Considering J values for nn, nnn, nnnn in honeycomb lattice
by Bheema Lingam Chittari 02 Jun '17

02 Jun '17

Dear Users, I would like to define three different J values for nearest neighbour (nn) next nearest neighbour (nnn) next to next nearest neighbour (nnnn) for honeycomb lattice. If I define J0, J1, J2 to the existing honeycomb lattice model (which is available in source files), is these are nothing but J values for nearest neighbour (nn) next nearest neighbour (nnn) next to next nearest neighbour (nnnn) for honeycomb lattice?. In other way, J0, J1, J2...... are they represent the nearest neighbour J values?? I did not got any information how J0, J1, J2..... will be considered in exiting lattices Please clarify Thank you Dr. Bheema Lingam Chittari Post Doctoral Researcher, Room No:14-115, Department of Physics, University of Seoul, 163 Seoulsiripdae-ro, Dongdumen-gu, Seoul, South Korea

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problem in reading custom-lattice.xml
by Bheema Lingam Chittari 02 Jun '17

02 Jun '17

Dear Users, Recently, I started using ALPS for Classical Monte Carlo with Python interface. I would like to do calculations for square-lattice with 1st (vertical), 2nd (horizantal) and 3rd (diagonal) nearest neighbours interactions J0, J1, J2. For the I have created a square-lattice.xml for 4x4 lattice. If I run the code in jupyter notebook, i am getting following error: parsing task files ... could not find graph/lattice specified in parameters: name was: 'Square_lattice' Please help me to find the error (I mean the xmal file written properly?), Do I need to do before I have to use my own xml file? My code is as follows: -------------------------------------------------------------------------------------------------------------------------------------------------------------------- import pyalps import matplotlib.pyplot as plt import pyalps.plot parms = [] for l in [16]: for t in [1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15]: parms.append( { 'LATTICE_LIBRARY' : "./Square-lattice.xml", 'LATTICE' : "Square_lattice", 'T' : t, 'S' : 2.62, 'J0' : 0.52 , 'J1' : -0.09 , 'J2' : 0.86 , 'THERMALIZATION' : 1000, 'SWEEPS' : 400000, 'UPDATE' : "local", 'MODEL' : "Ising", 'L' : l } ) input_file = pyalps.writeInputFiles('Square_isg',parms) pyalps.runApplication('spinmc',input_file,Tmin=10) pyalps.evaluateSpinMC(pyalps.getResultFiles(prefix='Square_isg')) data = pyalps.loadMeasurements(pyalps.getResultFiles(prefix='Square_isg'),['|Magnetization|', 'Specific Heat']) magnetization_abs = pyalps.collectXY(data,x='T',y='|Magnetization|',foreach=['L']) spec_heat = pyalps.collectXY(data,x='T',y='Specific Heat',foreach=['L']) #make plots plt.figure() pyalps.plot.plot(magnetization_abs) plt.xlabel('Temperature $T$') plt.ylabel('Magnetization $|m|$') plt.legend() plt.title('2D Ising model') plt.figure() pyalps.plot.plot(spec_heat) plt.xlabel('Temperature $T$') plt.ylabel('Specific Heat $c_v$') plt.legend() plt.title('2D Ising model') plt.show() ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ my xml file is below: ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ <LATTICES> <LATTICE name="Square_lattice" dimension="2"> <PARAMETER name="a" default="1"/> <PARAMETER name="b" default="1"/> <BASIS> <VECTOR>a 0</VECTOR> <VECTOR>0 b</VECTOR> </BASIS> <RECIPROCALBASIS> <VECTOR>2*pi/a 0</VECTOR> <VECTOR>0 2*pi/b</VECTOR> </RECIPROCALBASIS> </LATTICE> <UNITCELL name="simple2d" dimension="2" vertices = "4"> <VERTEX><COORDINATE> 0.0 0.0</COORDINATE></VERTEX> <VERTEX><COORDINATE> 0.5 0.0</COORDINATE></VERTEX> <VERTEX><COORDINATE> 0.0 0.5</COORDINATE></VERTEX> <VERTEX><COORDINATE> 0.5 0.5</COORDINATE></VERTEX> <EDGE type="0"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="2" offset="0.5 0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="3" offset="0 0.5"/></EDGE> <EDGE type="2"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="4" offset="0.5 0.5"/></EDGE> </UNITCELL> <LATTICEGRAPH name = "Square_lattice 4x4" > <FINITELATTICE> <LATTICE ref="Square_lattice"/> <EXTENT dimension="1" size="4"/> <EXTENT dimension="2" size="4"/> <BOUNDARY type="periodic"/> </FINITELATTICE> <UNITCELL ref="simple2d"/> </LATTICEGRAPH> </LATTICES> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Thank you in advance Dr. Bheema Lingam Chittari Post Doctoral Researcher, Room No:14-115, Department of Physics, University of Seoul, 163 Seoulsiripdae-ro, Dongdumen-gu, Seoul, South Korea

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