- Comp-phys-alps-users - lists.phys.ethz.ch

Quantum Wang-Landau algorithm question: applicability of QWL on frustrated lattices
by Prsa Krunoslav 02 Nov '09

02 Nov '09

Dear Prof. Troyer, Thanks for your answer. Yes, the lattice is 3D; and no, the frustration is not strong. I will follow your advice then: I'll try the QWL for the non-frustrated case, and with looper add points on the frustrated side of the phase diagram, if that will be feasible. All the best, Kruno > No, the current QWL code cannot do that. It is best to use the looper > code. Are you talking about 3D lattices? If frustration is strong the > sign problem will make simulations impossible at T_N. > Matthias > On 29 Oct 2009, at 12:20, Prsa Krunoslav wrote: > Dear ALPS maintainers, > Since nobody has yet answered to my questions from almost a month > ago, I will repeat just one question this time. > > Can the current incarnation of the QWL code handle frustrated > lattices? Specifically, I want to find the transition temperature as > a function T_N(J2/J1), where J2 and J1 are antiferromagnetic. > > > All the best, > Kruno > > --------------------------------------- > Krunoslav Prsa, Ph. D. Student > Laboratory for Neutron Scattering > Paul Scherrer Institute and ETH-Zürich > CH-5232 Villigen PSI, Switzerland > tel: +41 56 310 20 91 > mob: +41 76 386 17 99 > ---------------------------------------- > > > > -----Original Message----- > From: Prsa Krunoslav > Sent: Friday, October 02, 2009 2:56 PM > To: comp-phys-alps-users at phys.ethz.ch > Subject: Quantum Wang-Landau algorithm question: applicability of > QWL on (slightly) frustrated lattices > > > Dear ALPS maintainers, > > I have three questions with regards to your extremely powerful QWL > algorithm. > > 1. In the ALPS online documentation section for QWL algorithm there > is a note: > "Note: This first version allows the simulation of isotropic > Heisenberg spin-1/2 ferro- and antiferromagnetic models on arbitrary > non-frustrated lattices at zero magnetic field. In the future, we > plan to relax this constraint, and also provide an implementation of > the QWL perturbation expansion. " > > Has this been improved with regards to antiferro- frustrated > lattices? I am using ALPS version 1.3.3. > > 2. When I run the qwl for my slightly frustrated S=1/2 3D lattice > (consisting of triangular antiferro patterns J1-J1-J2 with J2~0.15 > J1) the program does not seem to complain (It does not seem to > complain even for the triangular lattice). Can its output for this > situation be trusted though? > > 3. I was also wondering if I can generally verify the results (say > T_N) of the frustrated model by an extrapolation from the non- > frustrated side (say ferro J2=-0.5,...,-0.1,0), thereby assuming a > mean-field like behaviour T_N~(J1-J2), for small J2. I am an > experimentalist so I may not be aware of this. Is there a general > result that would say it's not possible or at least a counterexample? > > It may be of relevance to some of the questions that in this lattice > there is a change in the classical ground state from Neel to the > triangular at J2=J1/3. > > All the best, > Kruno > > --------------------------------------- > Krunoslav Prsa, Ph. D. Student > Laboratory for Neutron Scattering > Paul Scherrer Institute and ETH-Zürich > CH-5232 Villigen PSI, Switzerland > tel: +41 56 310 20 91 > mob: +41 76 386 17 99 > ---------------------------------------- --------------------------------------- Krunoslav Prsa, Ph. D. Student Laboratory for Neutron Scattering Paul Scherrer Institute and ETH-Zürich CH-5232 Villigen PSI, Switzerland tel: +41 56 310 20 91 mob: +41 76 386 17 99 ----------------------------------------

2 1

Quantum Wang-Landau algorithm question: applicability of QWL on frustrated lattices
by Prsa Krunoslav 29 Oct '09

29 Oct '09

Dear ALPS maintainers, Since nobody has yet answered to my questions from almost a month ago, I will repeat just one question this time. Can the current incarnation of the QWL code handle frustrated lattices? Specifically, I want to find the transition temperature as a function T_N(J2/J1), where J2 and J1 are antiferromagnetic. All the best, Kruno --------------------------------------- Krunoslav Prsa, Ph. D. Student Laboratory for Neutron Scattering Paul Scherrer Institute and ETH-Zürich CH-5232 Villigen PSI, Switzerland tel: +41 56 310 20 91 mob: +41 76 386 17 99 ---------------------------------------- -----Original Message----- From: Prsa Krunoslav Sent: Friday, October 02, 2009 2:56 PM To: comp-phys-alps-users(a)phys.ethz.ch Subject: Quantum Wang-Landau algorithm question: applicability of QWL on (slightly) frustrated lattices Dear ALPS maintainers, I have three questions with regards to your extremely powerful QWL algorithm. 1. In the ALPS online documentation section for QWL algorithm there is a note: "Note: This first version allows the simulation of isotropic Heisenberg spin-1/2 ferro- and antiferromagnetic models on arbitrary non-frustrated lattices at zero magnetic field. In the future, we plan to relax this constraint, and also provide an implementation of the QWL perturbation expansion. " Has this been improved with regards to antiferro- frustrated lattices? I am using ALPS version 1.3.3. 2. When I run the qwl for my slightly frustrated S=1/2 3D lattice (consisting of triangular antiferro patterns J1-J1-J2 with J2~0.15 J1) the program does not seem to complain (It does not seem to complain even for the triangular lattice). Can its output for this situation be trusted though? 3. I was also wondering if I can generally verify the results (say T_N) of the frustrated model by an extrapolation from the non-frustrated side (say ferro J2=-0.5,...,-0.1,0), thereby assuming a mean-field like behaviour T_N~(J1-J2), for small J2. I am an experimentalist so I may not be aware of this. Is there a general result that would say it's not possible or at least a counterexample? It may be of relevance to some of the questions that in this lattice there is a change in the classical ground state from Neel to the triangular at J2=J1/3. All the best, Kruno --------------------------------------- Krunoslav Prsa, Ph. D. Student Laboratory for Neutron Scattering Paul Scherrer Institute and ETH-Zürich CH-5232 Villigen PSI, Switzerland tel: +41 56 310 20 91 mob: +41 76 386 17 99 ----------------------------------------

2 1

plotting...
by Muhammad Rofiq 29 Oct '09

29 Oct '09

Dear Mr. Troyer I've some problem to plot of LATTICE GRAPH, how to get a figure of my latticegraph? can it use xmgr? Thanks before, Akses email lebih cepat. Yahoo! menyarankan Anda meng-upgrade browser ke Internet Explorer 8 baru yang dioptimalkan untuk Yahoo! Dapatkan di sini! http://downloads.yahoo.com/id/internetexplorer

3 2

Extract data in 2D Heisenberg Model
by Simon Ketterer 24 Oct '09

24 Oct '09

Dear Matthias Troyer, For getting used with alps I've tried to extract the Spin Correlations location (index) and the Spin Correlations (mean value) itself of the 2D Heiseberg Model. Could you please suggest me how to insert the commands in the plot.xml file for extracting these data? I'd be very grateful if you could give some advice! Best regards Simon Ketterer TCD

2 1

spin interaction
by Muhammad Rofiq 04 Oct '09

04 Oct '09

Dear Mr. Troyer.. I've some problem about my Thesis, I would like to get solution about these.. my problems are: 1. Can the ALPS use to simulate spin interction and energy of CdMnTe? 2. if it can, what is the method to simulate spin interction and energy of CdMnTe? DMRG or the other method?and 3. what is the syntax program about it? Thanks before..... Lebih aman saat online. Upgrade ke Internet Explorer 8 baru dan lebih cepat yang dioptimalkan untuk Yahoo! agar Anda merasa lebih aman. Gratis. Dapatkan IE8 di sini! http://downloads.yahoo.com/id/internetexplorer/

1 0

Quantum Wang-Landau algorithm question: applicability of QWL on (slightly) frustrated lattices
by Prsa Krunoslav 02 Oct '09

02 Oct '09

Dear ALPS maintainers, I have three questions with regards to your extremely powerful QWL algorithm. 1. In the ALPS online documentation section for QWL algorithm there is a note: "Note: This first version allows the simulation of isotropic Heisenberg spin-1/2 ferro- and antiferromagnetic models on arbitrary non-frustrated lattices at zero magnetic field. In the future, we plan to relax this constraint, and also provide an implementation of the QWL perturbation expansion. " Has this been improved with regards to antiferro- frustrated lattices? I am using ALPS version 1.3.3. 2. When I run the qwl for my slightly frustrated S=1/2 3D lattice (consisting of triangular antiferro patterns J1-J1-J2 with J2~0.15 J1) the program does not seem to complain (It does not seem to complain even for the triangular lattice). Can its output for this situation be trusted though? 3. I was also wondering if I can generally verify the results (say T_N) of the frustrated model by an extrapolation from the non-frustrated side (say ferro J2=-0.5,...,-0.1,0), thereby assuming a mean-field like behaviour T_N~(J1-J2), for small J2. I am an experimentalist so I may not be aware of this. Is there a general result that would say it's not possible or at least a counterexample? It may be of relevance to some of the questions that in this lattice there is a change in the classical ground state from Neel to the triangular at J2=J1/3. All the best, Kruno --------------------------------------- Krunoslav Prsa, Ph. D. Student Laboratory for Neutron Scattering Paul Scherrer Institute and ETH-Zürich CH-5232 Villigen PSI, Switzerland tel: +41 56 310 20 91 mob: +41 76 386 17 99 ----------------------------------------

1 0

alps xml output & firefox 3x
by Evgeny Burovskiy 17 Sep '09

17 Sep '09

Gentlemen, I've noticed a little glitch recently: ALPS xml output is no longer displayed properly in the Firefox browser [I'm using FF 3.0.11 and 3.5 "Shiretoko"]. For in.xml files, which just list the task xml files, I get a blank page, while for the task*.out.xml files I have the contents but no formatting whatsoever, so that everything is displayed as a single line... Is it just my problem or is anybody else having this one too? And maybe somebody knows a fix or a workaround? I'm not sure if it is anyhow related to the address < http://xml.comp-phys.org/2003/8/job.xsd> in the header of alps xml files returning 404 Not Found error. Cheers, Zhenya

3 3

defining nonhomogeneous Hamiltonian on a homogeneous lattice
by Andriy Zhugayevych 13 Sep '09

13 Sep '09

Let you have the Hamiltonian "-t(i,j)*fermion_hop(i,j) + other terms" defined on any predefined in "lattices.xml" lattice, where "t" is some matrix, whose all elements are a priori different. The straightforward way to define this model is to define the graph with all its edges having different types. This solution looks fine for several defective bonds. But if all bonds are different (e.g. you want to optimize the geometry of kink-like solution of Hubbard-Peierls model), does more elegant way exist on application level? In any case it is worthwhile to place more comprehensive answer to this kind of questions in "Tutorials and Documentation/Definition of models" page. Kind regards, Andriy Zhugayevych

2 1

Units
by zhian asadzadeh 04 Sep '09

04 Sep '09

Hello All, what is unit for quantities which ALPS measures and use? such us magnetic field (h), Energy,.. Thanks, Zhian.

2 1

I've problem....
by Muhammad Rofiq 03 Sep '09

03 Sep '09

my name is Rofiq. I have a problem for the plotting magnetization graph of my reaserch... So, i would to ask" can The ALPS Used to plott magetization and temperature on a graph?" Lebih Bersih, Lebih Baik, Lebih Cepat - Rasakan Yahoo! Mail baru yang Lebih Cepat hari ini! http://id.mail.yahoo.com

2 1