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1244 discussions

Interaction involving three lattice sites
by Julien DESPRES 30 Aug '18

30 Aug '18

Dear ALPS community, I was wondering if it is possible to define an interaction involving three different lattice sites (for a 1D lattice model to perform dmrg calculations). To clarify, an example would be to construct the term \sum_i n_i n_{i+1} n_{i-1}. I checked in the doc if anyone had already the same kind of problem but it seems not. I guess that the solution is to build a bond term in the definition of the Hamiltonian by specifying the source and targets and to modify accordingly the lattice. Or is there a trick to specify one source (i) and two targets (i+1, i-1) ? Thanks in advance, Julien Ps : Just realized that I forgot to modify the subject (short vacations ...) -- __________________________________ DESPRES Julien Ph.D. student Center for Theoretical Physics Quantum Matter Theory team Ecole Polytechnique 91128 Palaiseau Cedex France, EU Office : 00.10.06 (ground floor) Phone : +33 1 69 33 42 81 Laboratoire Charles Fabry Atom Optics group Institut d'Optique Graduate School 2 Avenue Augustin Fresnel 91127 Palaiseau Cedex France, EU Office : R2.29 (1st floor) Phone: +33 1 64 53 33 49 __________________________________

2 1

What is the factor in Temperature unit when doing thermalization
by S Baidya 14 Aug '18

14 Aug '18

Dear Alps users, I tried to look into the examples and files in the alps directory to find the actual factor of temperature variable (T). In magnetization vs temperature plot in the example number mc-07 the plot shows temperature range of 0 to 5 in Kelvin. I need to know if the T is exactly T or with same factor. Where can I find the program to specify this details. Sometime T should be around 300-4000 K kelvin range but it still shows temperature around 5 - 8 Kelvin . Thank you, Santu Baidya

2 6

ALPS code error with Kagome spin lattice to calculate susceptibility
by S Baidya 08 Aug '18

08 Aug '18

Dear Alps users, I am totally new to ALPS code using quantum monte carlo. I have started to use this code for few small purpose like magnetic suceptibility vs temperature for various spin lattice models. Currently I have used ALPS code for calculating susceptibility for ising type S=3/2 Kagome lattice. I found in the lattice library that Kagome lattice is defined. So in the tutorial mc-02-susceptibilities/ I changed tutorial2d.py by editing #prepare the input parameters parms = [] for t in [0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.25, 1.5, 1.75, 2.0]: parms.append( { 'LATTICE' : "Kagome lattice", 'MODEL' : "spin", 'local_S' : 1.5, 'T' : t, 'J' : 4.2 , 'THERMALIZATION' : 5000, 'SWEEPS' : 50000, 'L' : 60, 'ALGORITHM' : "loop" } ) Then I changed the same way param2d file and ran the alpspython tutorial2d.py and I got strange error /usr/local/lib/python2.7/dist-packages/matplotlib/style/core.py:203: UserWarning: In /usr/share/matplotlib/stylelib/classic.mplstyle: text.dvipnghack is obsolete. Please remove it from your matplotlibrc and/or style files. warnings.warn(message) loop parm2d.in.xml ALPS/looper version 3.2b12-20100128 (2010/01/28) multi-cluster quantum Monte Carlo algorithms for spin systems available from http://wistaria.comp-phys.org/alps-looper/ copyright (c) 1997-2010 by Synge Todo <wistaria(a)comp-phys.org> using ALPS/parapack scheduler a Monte Carlo scheduler for multiple-level parallelization copyright (c) 1997-2016 by Synge Todo <wistaria(a)comp-phys.org> based on the ALPS libraries version 2.3.0 available from http://alps.comp-phys.org/ copyright (c) 1994-2016 by the ALPS collaboration. Consult the web page for license details. For details see the publication: B. Bauer et al., J. Stat. Mech. (2011) P05001. [2018-Aug-03 14:02:51]: starting scheduler on cces-System-Product-Name master input file = /home/cces/kagome-alps/mc-02/parm2d.in.xml master output file = /home/cces/kagome-alps/mc-02/parm2d.out.xml termination file = [disabled] total number of thread(s) = 1 thread(s) per clone = 1 number of thread group(s) = 1 auto evaluation = yes time limit = unlimited interval between checkpointing = 3600 seconds interval between progress report = 600 seconds interval between vmusage report = infinity task range = all worker dump format = hdf5 worker dump policy = running workers only [2018-Aug-03 14:02:51]: task status: total number of tasks = 15 new = 15, running = 0, continuing = 0, suspended = 0, finished = 0, completed = 0, skipped = 0 [2018-Aug-03 14:02:51]: starting 1 threadgroup(s) [2018-Aug-03 14:02:51]: dispatching a new clone[1,1] on threadgroup[1] WARNING: model is classically frustrated WARNING: model has negative signs I donot understand the actual reason and how to solve this situation. I used this tutorial before and it worked for ladder spin lattice. Can anyone please tell me what should I do to solve this situation. Thanking you, Santu Baidya

3 12

Problem in installing ALPS code in Ubuntu
by S Baidya 21 Jul '18

21 Jul '18

Dear ALPS users, I have downloaded alps-2.2.b4-src-with-boost.tar.gz in my linux pc with Ubuntu. I installed required python packages python2.7. I then untar by tar -xvzf alps-2.2.b4-src-with-boost.tar.gz Then mkdir build Then cd build Then cmake -DCMAKE_INSTALL_PREFIX=/home/cces/Downloads/ALPS/alps-2.2.b4-src-with-boost/alps/ .. I got an error. I tried different ways too using conda install but it did not work. So, I thought to build from source in linux as suggested in some websites. I have attached the Log file of the error. Can anyone please help me to install the alps in linux pc. I sent this mail before but I found there was an issue with maximum size of mail. So I have attached only one error file. Thanking you, Santu

4 20

vispython not found in recently installed alps-2.3 in Ubuntu !
by S Baidya 20 Jul '18

20 Jul '18

Dear alps users, After struggling I just installed alps-2.3 in Ubuntu . I build the alps-2.3 successfully. Now i was trying to do some tutorials in the directory ./alps-2.3.0-src-with-boost/alps/tutorials by runing the executable ./runtutorial.sh which fails saying /runtutorial.sh: 10: ./runtutorial.sh: vispython: not found ./runtutorial.sh: 10: ./runtutorial.sh: vispython: not found What should I do. Is there anything else needed to install to install alps successfully and use it for application. Please tell me to solution to use alps without error. Thanks, Santu

1 0

Reducing the number of correlation calculations in a run?
by PRADEEP 02 Jul '18

02 Jul '18

Dear ALPS community, I am using the DMRG programs (with OBC) to calculate the spin-spin correlations of a spin chain. Suppose N is the number of sites in the chain. My question is - while using the DMRG programs, is it possible to restrict calculations of correlations to a distance "d" between two sites where d<<N? Eg. instead of calculating all the N**2 correlations between all the spins, calculate only nearest neighbours or N-1 correlations? I want to obtain correlations for N>128 sites. ~60GB of RAM on a workstation is proving insufficient for this. I have been able to obtain local spin components <S_i^a> (a=x,y,z) for N=512 too. But, for the correlation calculations, N**2 correlations require more than 4 times the available RAM even for N=128. So I have to use smaller N, which leads to pronounced effects due to finite size and boundaries. Hence, the question. Thanks very much. with regards, Pradeep Thakur.

1 0

Potts Model - Classical Monte Carlo
by Dave Maren 17 May '18

17 May '18

Dear alps users and developers, Lately I have been exploring the behavior of the Potts model for a small classic system (square lattice) but I have a doubt about the results I get. As a method of checking I am using my own Monte Carlo and I find that there are differences with respect to what the ALPS give me. For example, the energy of the system at high temperatures should tend to zero due to the disorder caused by the thermal energy, result that I get with my Monte Carlo and approximate methods of the partition function, however, with the ALPS I obtain a stabilization of energy around negative values far away by several units from the zero and a different behavior in terms of the energy evolution (shape of the curve). I would like to know what kind of states are considered for the Potts model q = 3, q = 4 and what could be causing these differents results that I am obtaining. Thank you very much

1 0

Facing problems with TEBD
by Paolo Mazza 24 Apr '18

24 Apr '18

Dear All, I’ ve just installed Alps using Conda (on a OSX). I tried to run several tutorials and they all work. But I am facing problems with the tebd package. When I try to run the tutorials concernig the tebd appears this error "/bin/sh: tebd: command not found” how can I fix it? Thank you very much in advance Paolo P.

2 1

XXZ model with transverse field (Gamma) and Jz<1
by pradeep 06 Apr '18

06 Apr '18

Hello All, I have been trying to reproduce a result from these two papers: https://journals.jps.jp/doi/10.1143/JPSJ.64.3409 and https://arxiv.org/abs/cond-mat/0403035v3 using the dmrg code from alps-2.1.1-r6176-src-with-boost. I have a reason to use this older version, which I'll elaborate on later. The Heisenberg XXZ model, with Ising anisotropy Jz<1, in the presence of a transverse field hx (Gamma in the models.xml file), shows a staggered magnetization in the y-direction, for hx < h_c. h_c is roughly sqrt(2*(1+Jz)). (Ref. the above two papers.) In the models file, <SITEOPERATOR name="Sy" site="x"> (1/(2*I))*(Splus(x)-Sminus(x)) </SITEOPERATOR> I set Jz = 0.25, Jxy = 1, Gamma (or hx) = 1.1 (which is < h_c for the given Jz) and chain length = 64, with open boundary conditions. MAXSTATES=70 and SWEEPS=10. I measure local Sy and then after the data have been generated, calculate the staggered average, by summing over the local expectation values for all sites, with alternating weights +1 and -1. However, the measured local <Sy> is identically zero for all sites. So the staggered average also turns out to be zero. ---> first discrepancy - Staggered Magnetization in y should have been non-zero. - - - - The XXZ chain has spin-rotation symmetry in the spin-XY plane, so whether we define hx as the transverse field (with hz = hy = 0) or hy as the transverse field (with hx = hz = 0), we expect to get the same results, theoretically. So the XXZ chain with hy = 1.1 (hz=hx=0) should yield a staggered magnetization in the x-direction. To check this, I added -hy#*Sy(i) in the site term of the "spin" Hamiltonian in the models file. Now I get a staggered magnetization in the x-direction, as expected theoretically. I then removed the restriction of "alps::numeric::real" from the dmrg.h and measurement_operators.h files and recompiled alps, so that I can check the real and imaginary parts of the expectation values of Splus and Sminus and see whether these match with the corresponding expectation values of Sx and Sy respectively. Case 1: For hx = 1.1 (h=hy=0), the expectation values for the zeroth site of the chain are: Sx(0) = (0.432462,0) Sy(0) = (0,1.52059e-17) Splus(0) = (0.432462,0) Sminus(0) = (0.432463,0) Case 2: For hy = 1.1 (h=hx=0), these are: Sx(0) = (-0.157932,-1.64072e-18) Sy(0) = (0.43251,5.62317e-19) Splus(0) = (-0.157932,0.43251) Sminus(0) = (-0.157932,-0.43251) For case 1, the imaginary parts of the expectation values of Splus and Sminus for the zeroth site are zero (for all sites). Consequently, Sy is also identically zero for all sites, which is not expected on theoretical grounds. The Sx value is as expected. For case 2, the real and imaginary parts of Splus and Sminus are giving the expected values of Sx and Sy, atleast qualitatively. ---> second discrepancy - Transverse fields hx and hy are giving different results; error in the measurement of the imaginary parts of Splus and Sminus. - - - - I request the ALPS community to look into this issue. These discrepancies have not been resolved in the newer releases of alps (2.2.b3-r7462, 2.2.b4 and 2.3.0) either. In fact, the newer versions do not give reasonable results for the XXZ chain with transverse field at all (atleast for the parameters chosen above). Do let me know if there's any possible work-around or if there's Anything I could do in the code's modules to make things work as expected. With best regards to the entire community, Pradeep Thakur.

1 0

pyrochlore lattice
by kadowaki＠tmu.ac.jp 27 Mar '18

27 Mar '18

Dear All, I made a definition of the pyrochlore lattice (lattices.xml) and put it at a repository https://github.com/kadowaki-h/LatticesPyrochloreCubic. A simple example of calculating specific heat C(T, H=0) of the NN Spin Ice model is also given in the repository. Best wishes, Hiroaki Kadowaki Department of Physics, Tokyo Metropolitan University Hachioji-shi, Tokyo 192-0397, Japan kadowaki(a)tmu.ac.jp

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