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Structure factor again
by Jean-David Picon 19 Apr '07

19 Apr '07

Hi, I am still in trouble with my unitcell and lattice. My unitcell is defined as follows <UNITCELL name="dimerZ" dimension="3"> <VERTEX type="1"> <COORDINATE> 0 0 0</COORDINATE> </VERTEX> <VERTEX type="2"> <COORDINATE> 0 0 1 </COORDINATE> </VERTEX> <EDGE type="0"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="2" offset="0 0 0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="1" offset="1 0 0"/></EDGE> <EDGE type="2"><SOURCE vertex="2" offset="0 0 0"/><TARGET vertex="2" offset="1 0 0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="1" offset="0 1 0"/></EDGE> <EDGE type="2"><SOURCE vertex="2" offset="0 0 0"/><TARGET vertex="2" offset="0 1 0"/></EDGE> </UNITCELL> and describes 2 spins oriented ALONG THE Z axe. In order to have one layer of these pairs AND structure factor results in 3D with sse, I choose a 3D cubic lattice of height 1. (If I choose a 2D cubic lattice, I just get e.g. (pi, pi) structure factor and not (pi,pi,X)). The problem : the structure factor results are only (X,X,0) results. I do not have for example (pi,pi,pi) SF whereas my system is really 3D. Any help to understand why is welcome ! Thanks, Jean-David

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Structure factor and unit cell
by Jean-David Picon 16 Apr '07

16 Apr '07

Hi, Regarding my last questions, if I put 2 vertices in the unit cell without giving their respective positions, what is then the meaning of the structure factor calculated by ALPS ? In other words, what positions of the 2 spins does ALPS use ? Finally, if I give these positions, will I get the structure factor of the crystal of spins ? Thanks a lot. Jean-David

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Unitcell and graphs
by Jean-David Picon 11 Apr '07

11 Apr '07

Hi, I am trying to build a lattice composed of 2 layers of spins where the spins of layer 1 do not play the same role (ie the next neighbour edges J//1 and J//2 in the layers are different) as those in the layer 2. I guess I cannot just use an "anisotropic 3d" latticegraph so I am trying with a unitcell with 2 spins. Can I just create a unitcell as follows <UNITCELL name="dimer_along_Z" dimension="3"> <VERTEX type="1"> <COORDINATE> 0 0 0</COORDINATE> </VERTEX> <VERTEX type="2"> <COORDINATE> 0 0 1 </COORDINATE> </VERTEX> <EDGE type="0"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="2" offset="0 0 0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="1" offset="1 0 0"/></EDGE> <EDGE type="2"><SOURCE vertex="2" offset="0 0 0"/><TARGET vertex="2" offset="1 0 0"/></EDGE> <EDGE type="3"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="2" offset="1 0 0"/></EDGE> <EDGE type="4"><SOURCE vertex="2" offset="0 0 0"/><TARGET vertex="2" offset="1 0 0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="1" offset="0 1 0"/></EDGE> <EDGE type="2"><SOURCE vertex="2" offset="0 0 0"/><TARGET vertex="2" offset="0 1 0"/></EDGE> <EDGE type="3"><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="2" offset="0 1 0"/></EDGE> <EDGE type="4"><SOURCE vertex="2" offset="0 0 0"/><TARGET vertex="2" offset="0 1 0"/></EDGE> </UNITCELL> and then choose a 2d lattice as LATTICE ? Thanks, Jean-David

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parameter values
by bkeith＠clarku.edu 10 Apr '07

10 Apr '07

Hello, I am using alps version 2 and I have been trying to compare some simulations to experimental data but I can't find out what the units on the parameters are. Is this written somewhere? For instance, is Temperature in kelvin and is the exchange strength J in units of energy or kelvins? -Brian Keith

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Tools
by Jean-David Picon 10 Apr '07

10 Apr '07

Hi, Two questions about extracting data from the output files of dirloop_sse calculations. 1- I used the convert2html tool on a .task*.out.xml file but it would be even more useful if I could convert a whole archive file to html. Is this possible ? 2- Can we build "multiple"plots that is to say not only one y-axis but more e.g. h Mz Stiffness 6.0 31 ... ... ... ... Many thanks, Jean-David Picon

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MC heisenberg follow up/ lattices
by David Miller 09 Apr '07

09 Apr '07

Hi, Thanks for the reply. I would also like to know if the anisotropy can be varied throughout the lattice, i.e. different values for different sites, or is only one value throughout the whole lattice allowed? Additionally I would like some points regarding the lattice definitions to be confirmed. 1. The edge type 0,1,2 corresponds to bond type J0, J1 ,J2 parameters? Edge type default = 0? 2. The edge offset is in units of 'basis vectors' specified in the <BASIS> tags? Default = 0 0 0? Allowing both -ve and +ve numbers? Thanks, David Miller >From: comp-phys-alps-users-request(a)phys.ethz.ch >Reply-To: comp-phys-alps-users(a)phys.ethz.ch >To: comp-phys-alps-users(a)phys.ethz.ch >Subject: Comp-phys-alps-users Digest, Vol 12, Issue 2 >Date: Wed, 28 Mar 2007 12:00:02 +0200 > >Send Comp-phys-alps-users mailing list submissions to > comp-phys-alps-users(a)phys.ethz.ch > >To subscribe or unsubscribe via the World Wide Web, visit > https://webmail.phys.ethz.ch/mailman/listinfo/comp-phys-alps-users >or, via email, send a message with subject or body 'help' to > comp-phys-alps-users-request(a)phys.ethz.ch > >You can reach the person managing the list at > comp-phys-alps-users-owner(a)phys.ethz.ch > >When replying, please edit your Subject line so it is more specific >than "Re: Contents of Comp-phys-alps-users digest..." > > >Today's Topics: > > 1. Re: Classical MC Heisenberg help (Matthias Troyer) > > >---------------------------------------------------------------------- > >Message: 1 >Date: Tue, 27 Mar 2007 17:23:54 +0200 >From: Matthias Troyer <troyer(a)phys.ethz.ch> >Subject: Re: [ALPS-users] Classical MC Heisenberg help >To: comp-phys-alps-users(a)phys.ethz.ch >Message-ID: <531DC60A-E501-4263-ACD0-ECD3FF56F0CB(a)phys.ethz.ch> >Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed > >It should work by specifying the parameter > >D="0 0 1" > >The three components are Dx, Dy and Dz. Please be aware however that >in that case only local updates can be used. > > >Matthias > > >On Mar 27, 2007, at 1:30 AM, David Miller wrote: > > > Dear all, > > > > I am doing classical MC simulations using the Heisenberg model with > > Alps-1.3b2. I would like to include an easy axis/plane anisotropy > > in the Heisenberg Hamiltonian of the form (-/+)D*sum_i((Sz_i)^2), > > how would I acheive this? > > > > Thanks, > > > > David Miller > > > > _________________________________________________________________ > > Solve the Conspiracy and win fantastic prizes. http:// > > www.theconspiracygame.co.uk/ > > > >End of Comp-phys-alps-users Digest, Vol 12, Issue 2 >*************************************************** _________________________________________________________________ Solve the Conspiracy and win fantastic prizes. http://www.theconspiracygame.co.uk/

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Re: [ALPS-users] changing parameters in ALPS
by Matthias Troyer 29 Mar '07

29 Mar '07

Hi Aniket, The answer is simple: add a line like S=2 to the parameters. However there should generally be no need, since the value of S can just be absorbed into the coupling constant. Best regards Matthias On 29 Mar 2007, at 20:50, aniket(a)jncasr.ac.in wrote: > Respected sir, > I am new user of ALPS. So can I ask you one query? > > How change the value of S in 1D Heisenberg model? > > Hamiltonian for 1D Heisenberg model > > H = sum (S(i)*S(j)) > > description > > here H is the Hamiltonian > > sum means summation over all i & j. > > S(i) and S(j) means i & j th spin. > > by default S value is 1 for classical CONVENTION. > how change this value (other than 1)? > > I am running alps-application/tutorial/classical2/parm2a file. > > ( for convenience I am attaching URL also > http://alps.comp-phys.org:16080/mediawiki-1.9.3/index.php/ > Tutorial:ClassicalMCSimulations#The_one-dimensional_Heisenberg_chain ) > > I am waiting for your reply. > > Regards, > Aniket

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Classical MC Heisenberg help
by David Miller 27 Mar '07

27 Mar '07

Dear all, I am doing classical MC simulations using the Heisenberg model with Alps-1.3b2. I would like to include an easy axis/plane anisotropy in the Heisenberg Hamiltonian of the form (-/+)D*sum_i((Sz_i)^2), how would I acheive this? Thanks, David Miller _________________________________________________________________ Solve the Conspiracy and win fantastic prizes. http://www.theconspiracygame.co.uk/

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Re: [ALPS-users] ALPS questions: triangular lattice basis vectors, spatially anisotropic model
by Simon Trebst 16 Feb '07

16 Feb '07

Dear Fa, thanks for your email. (1) Indeed the second vector in the triangular lattice description is incorrect and should be replaced by <VECTOR>a/2 a*sqrt(3)/2</VECTOR> We have changed this in the code repository (it will become available with the next release). So please update this line in your current files for the time being. (2) Yes, you can already implement spatially anisotropic models with different interaction terms on different types of bonds. The <BONDTERM> has a type-variable which allows this. Here is an example from the model library how-to webpage (http://alps.comp-phys.org: 16080/wiki/index.php/Tutorials:ModelHOWTO) for a Bose Hubbard model: <HAMILTONIAN name="hardcore boson"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t" default="1"/> <PARAMETER name="t'" default="1"/> <BASIS ref="hardcore boson"/> <SITETERM type="0"> -mu*n </SITETERM> <BONDTERM type="0" source="i" target="j"> -t*(bdag(i)*b(j)+bdag(j)*b(i))) </BONDTERM> <BONDTERM type="1" source="i" target="j"> -t'*(bdag(i)*b(j)+bdag(j)*b(i))) </BONDTERM> </HAMILTONIAN> If you implement a new (triangular) lattice with two different type of bonds, e.g. "0" and "1", and implement your Hamiltonian similar to the one above, will you be able to study the model you are interested in? Please let me know, and we can further assist you Simon PS: I have copied this email to the ALPS user mailing list. > Dear Dr. Trebst > > I'm a graduate student in physics department at berkeley. > Currently i'm trying to learn to use the ALPS library and > application and have met some problems. > > I'm not sure whether you are the right person to contact. > If not, please ignore the following and take my apology. > > (1). In the lattices.xml library, the triangular lattice is > <LATTICE name="triangular lattice" dimension="2"> > <PARAMETER name="a" default="1"/> > <BASIS> > <VECTOR>a 0</VECTOR> > <VECTOR>a*sqrt(3)/2 a/2</VECTOR> > </BASIS> > <RECIPROCALBASIS> > <VECTOR>0 4*pi/a/sqrt(3)</VECTOR> > <VECTOR>2*pi/a -2*pi/a/sqrt(3)</VECTOR> > </RECIPROCALBASIS> > </LATTICE> > > The 2nd basis vector (a*sqrt(3)/2, a/2) doesn't look correct to > me. Or > maybe I misunderstood how it is represented. > > (2). In the tutorial I can't find out how to make spatially > anisotropic model. For example, anisotropic triangular Heisenberg > antiferromagnet. > It seems that the <BONDTERM> doesn't care the type of bond, or > the type of source/target sites. > Does this kind of feature have been incorporated into the > applications, > or do I have to write my own code to implement this? > > Thank you for your help. > > Best regards. > > ~Fa

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Modifying input in the DMRG program
by Christopher Brust 16 Feb '07

16 Feb '07

Hi. I'm a student doing research on Heisenberg spin chains, and I'm attempting to get ground state energies for longer chains than my group has done before. I've been running the DMRG program included with ALPS (not the 'simple' one) with a parameter file that looks something like: MODEL = "spin" LATTICE = "chain lattice" LATTICE_LIBRARY = "../lattices.xml" MODEL_LIBRARY = "../models.xml" CONSERVED_QUANTUMNUMBERS = "Sz" local_S = 1/2 J = 1 V = 0 SWEEPS = 30 MAXSTATES = 60 OUTPUT_LEVEL = 1 {L = 30} I've been able to successfully run the program, though I'm not entirely sure that all the parameters I've specified are the right ones (and that it's not just reverting to the defaults). I've been unable to find any documentation on how this particular implementation of the program works, so can anyone tell me if I'm off to the right start? In addition, I'd like to be able to run this program with site-dependent interaction coefficients (such as J = 3*k) or so, but after much tinkering, I've been unable to find the variable 'k' that represents position on the lattice. My question is is this even possible? If so, how? Should I instead be trying to modify the source code for the program and recompile it? Thanks for your time.

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