Comp-phys-alps-users

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1244 discussions

Maybe "honeycomb" definition is wrong in lattice lib (lattices.xml)
by kaveh edalat 01 Nov '12

01 Nov '12

Dear All I like to make a graphene bilayer. I wanted to use "honeycomb" definition in the lattice library but I found something strange! The strange thing is the definition of vertexes: <UNITCELL name="honeycomb" dimension="2"> <VERTEX><COORDINATE>0 0</COORDINATE></VERTEX> <VERTEX><COORDINATE>-0.288665771484375 0.5773468017578125</COORDINATE></VERTEX> ....... ...... </UNITCELL> I don't know how these two numbers "-0.288665771484375 0.5773468017578125" were generated ( they are near to "-1/(2*sqrt(3)), 1/sqrt(3)" !) I think if we suppose the vertex coordinate is defined according to the lattice vectors (.i.e. a1=[1 0], a2=[1/2 sqrt(3)/2]), then the correct numbers should be: "-1/3, 2/3" (-1/3*a1+2/3*a2). So the correct "UNITCELL" should be: <UNITCELL name="honeycomb" dimension="2"> <VERTEX><COORDINATE>0 0</COORDINATE></VERTEX> <VERTEX><COORDINATE>-1/3 2/3</COORDINATE></VERTEX> ....... ...... </UNITCELL> I checked the new "UNITCELL", and I found the lattice is more like to graphene. If I am wrong please correct me. Thanks Kaveh Edalat

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Edit Complex number
by Forwordom 30 Oct '12

30 Oct '12

2 1

How can we visualize a lattice in ALPS?
by kaveh edalat 30 Oct '12

30 Oct '12

Dear All I want to make a new lattice, but before serious calculation, I like to see the lattice. I searched in the alps mailing list and I found that probably "lattice-preview" should be a tool for visualization of lattices in ALPS. But I have two problem: first, when simply I type "lattice-preview" in the terminal I receive the following error: /opt/alps/bin/lattice-preview: 30: /opt/alps/lib/python/alps/preview.py: Permission denied Is there anyone to know why I receive the error? second, If we suppose the "lattice-preview" works well, what is the input file for this program? thanks in advanced Kaveh Edalat

2 1

Covariance matrix of RealVectorObservable
by Giuseppe Carleo 29 Oct '12

29 Oct '12

Dear all, I have got a question about the calculation of the covariance matrix of a vector observable (RealVectorObservable type, for example): Indeed I am able to compute the (jacknife-corrected) simple covariance of two given scalar observables in this simple way --------------- string filename = "simulation.task1.out.h5"; mcdata<double> obs1; mcdata<double> obs2; obs1.load(filename, "simulation/results/" + alps::hdf5_name_encode("Observable1")); obs2.load(filename, "simulation/results/" + alps::hdf5_name_encode("Observable2")); cout << "Covariance: " << obs1.covariance(obs2) << "\n\n"; --------------- However it is not entirely clear to me how to proceed when one instead has a single vector observable recorded in the hdf5 file and wants to compute to covariance matrix of its entries. In that case mcdata cannot be used any longer and digging into the code source I did not manage to find a method "covariance" implemented for other than mcdata-like scalar observables. Is there a handy solution already implemented for that? Thank you in advance! Regards, Giuseppe

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Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 79, Issue 6
by Forwordom 29 Oct '12

29 Oct '12

2 1

Edit Complex number
by Forwordom 28 Oct '12

28 Oct '12

Hi alps users and developers I want to simulate a lattice phase transition in external magnetic along x,y,z direction by using dmrg.I have to couple site operator with external magnetic field. But how to edit a complex number in the ALPS models.xml to get site operator Sy=1/2i(Splus-Sminus). Thanks in advance for your reply.

2 1

Imaginary Operators and advanced correlation functions
by zhian asadzadeh 27 Oct '12

27 Oct '12

Dear ALPS users, I have two questions regarding DMRG application of ALPS; 1. is it possible to define imaginary operators in this new version? in the simplest case I tried for operator like Sy=1/(2*I)(S+-S-) and it seems doesn't recognise I, how should i define the imaginary part? 2. I am interested to calculate correlations like <O1O2O3> in which O's are local operators and they could be also imaginary like Sy in (<Sx(i)Sy(j)Sz(k)>? I know at the moment just correlations like <O1O2> are calculable, but I would like to know is it easy to implement the above mentioned problem or is there a kind of trick to do it? -- Sincerely yours, Zhian.

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spinmc questions
by Jonas Anderson 22 Oct '12

22 Oct '12

I have some very basic questions for which I cannot find documented answers. (1) For the Ising models or more generally for classical spin models is it possible to view the final spin configuration of a system after the simulation has run its course? (2) Is it possible to observe the magnetization and not just the absolute value of the magnetization? Thanks in advance, -jonas -- Jonas T. Anderson Post-doc Université de Sherbrooke

2 3

tmp directory for DMRG
by benoît grémaud 19 Oct '12

19 Oct '12

Dear All, I would like to know if one can change, at runtime, the directory for temporary files used by the DMRG code. /tmp is the current location, but my / partition is rather small and get filled rapidly for large system sizes. thank you for your help. (i am using alps-2.1.1-r6176) regards, Benoît Grémaud -- -------------------- Researcher at CNRS, Laboratoire Kastler Brossel (Paris, France) Visiting Associate Professor at the Centre for Quantum Technologies (NUS, Singapore)

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question about ALPS
by hamid mosadegh 11 Oct '12

11 Oct '12

Dear ALPS user is it possible to define a distance dependent terms to Hamiltonians ,like this term, V/|i-j| I try to define this term but the program can not evaluate i & j. thanks in advance -- -- H. Mosadeq Ph.D. student of Physics, Isfahan Univ. of Technology, Isfahan 84156, Isfahan, IRAN

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