Dear users,
I'm trying to perform classical MC simulation for the 3D Heisenberg model. The model is formed by random magnetic impurities in periodic lattice interacting with different Jij for various neighboring distances r between the magnetic sistes (i and j).
Any suggestions on how to define different J's between different sites?
Thanks a lot,
Gianni
Hi Gianni - I think it depends a bit on what you mean. If you only have a small, finite number of couplings in your problem (e.g. J1,J2,J3,J4,J5) and the model preserves translation invariance, then you can simply add extra bonds to your lattice definition in order to define further neighbor couplings (see example 1 below).
However, if you would like to explicitly generate a random coupling constant for each bond (that is, the number of unique couplings in your problem scales with the system size) then one way you could proceed is to write a script to explicitly create the lattice XML file, giving each different bond a unique number (see example 2 below). You would then have to put J1=1.23423; J2 = -0.234; ... J120 = 2.3; etc. in your parameter file and specify LATTICE="lattice_name" and LATTICE_LIBRARY="lattice_filename.xml" as well.
Example 1 - Translationally Invt <UNITCELL name="J3 triangular" dimension="2"> <VERTEX/> <EDGE type ="1"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="1" offset="0 1"/></EDGE> <EDGE type ="1"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="1" offset="1 0"/></EDGE> <EDGE type ="1"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="1" offset="-1 1"/></EDGE> <EDGE type ="3"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="1" offset="0 2"/></EDGE> <EDGE type ="3"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="1" offset="2 0"/></EDGE> <EDGE type ="3"><SOURCE vertex="1" offset="0 0"/><TARGET vertex="1" offset="-2 2"/></EDGE> </UNITCELL>
[N.B. For this to work the "triangular lattice" lattice must also be defined in your lattices.xml file] <LATTICEGRAPH name = "J3 triangular lattice"> <FINITELATTICE> <LATTICE ref="triangular lattice"/> <PARAMETER name="W" default="L"/> <EXTENT dimension="1" size="L"/> <EXTENT dimension="2" size="W"/> <BOUNDARY type="periodic"/> </FINITELATTICE> <UNITCELL ref="J3 triangular"/> </LATTICEGRAPH>
Example 2 - Explicit Definition <LATTICES> <GRAPH name="Disordered_Lattice_Name" vertices="1000"> <VERTEX id="1" type="0"> <COORDINATE> 3.625 1.125 3.125 </COORDINATE> </VERTEX> <VERTEX id="2" type="0"> <COORDINATE> 3.625 0.625 2.625 </COORDINATE> </VERTEX> <VERTEX id="3" type="0"> <COORDINATE> 0.625 1.625 0.625 </COORDINATE> </VERTEX> [.....] <VERTEX id="1000" type="0"> <COORDINATE> 0.125 3.625 0.125 </COORDINATE> </VERTEX>
<EDGE type="1" source="1" target="1406"/> <EDGE type="2" source="1" target="1126"/> <EDGE type="3" source="1" target="1196"/> <EDGE type="4" source="1" target="517"/> [... N.B. the type=".." numbers can be the same or different] <EDGE type="5" source="2" target="692"/> <EDGE type="6" source="2" target="722"/> <EDGE type="7" source="2" target="980"/> <EDGE type="8" source="2" target="505"/> [...] /GRAPH> </LATTICES>
On Fri, Apr 3, 2009 at 9:41 AM, Gianni Profeta gianni.profeta@aquila.infn.it wrote:
Dear users,
I'm trying to perform classical MC simulation for the 3D Heisenberg model. The model is formed by random magnetic impurities in periodic lattice interacting with different Jij for various neighboring distances r between the magnetic sistes (i and j).
Any suggestions on how to define different J's between different sites?
Thanks a lot,
Gianni
Dear Users,
Consider a system with different magnetic sites but the crystallographic occupation factor of some of them is less than 1.0 (lets say 0.5). How can we describe this in the lattices.xml file where we develop the unitcell?
Kind regards,
Vassilis
----------------------------------------------------------------- Vassilis Tangoulis Lecturer in Inorganic Chemistry Laboratory of Inorganic Chemistry, Department of Chemistry Aristotle University of Thessaloniki, 54124 Thessaloniki,GREECE Tel : +30 2310 997 676 Fax : +30 2310 997 738 Email: vtagkoul@chem.auth.gr =================================================================
Dear Vassilis,
is this occupation of 0.5 regular, in a pattern, or random?
Matthias
On Apr 5, 2009, at 10:03 AM, Vassilis Tangoulis wrote:
Dear Users,
Consider a system with different magnetic sites but the crystallographic occupation factor of some of them is less than 1.0 (lets say 0.5). How can we describe this in the lattices.xml file where we develop the unitcell?
Kind regards,
Vassilis
Vassilis Tangoulis Lecturer in Inorganic Chemistry Laboratory of Inorganic Chemistry, Department of Chemistry Aristotle University of Thessaloniki, 54124 Thessaloniki,GREECE Tel : +30 2310 997 676 Fax : +30 2310 997 738 Email: vtagkoul@chem.auth.gr =================================================================
Dear Matthias,
The occupation factor is regular.. (i.e. every unit cell there is 0.5 of a particular magnetic site!)
Regards,
Vassilis
-----Original Message----- From: comp-phys-alps-users-bounces@phys.ethz.ch [mailto:comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer Sent: Sunday, April 05, 2009 11:49 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] Occupation factor
Dear Vassilis,
is this occupation of 0.5 regular, in a pattern, or random?
Matthias
On Apr 5, 2009, at 10:03 AM, Vassilis Tangoulis wrote:
Dear Users,
Consider a system with different magnetic sites but the crystallographic occupation factor of some of them is less than 1.0 (lets say 0.5). How can we describe this in the lattices.xml file where we develop the unitcell?
Kind regards,
Vassilis
Vassilis Tangoulis Lecturer in Inorganic Chemistry Laboratory of Inorganic Chemistry, Department of Chemistry Aristotle University of Thessaloniki, 54124 Thessaloniki,GREECE Tel : +30 2310 997 676 Fax : +30 2310 997 738 Email: vtagkoul@chem.auth.gr =================================================================
What do you mean by 0.5? how can you have half a site?
On 5 Apr 2009, at 20:03, Vassilis Tangoulis wrote:
Dear Matthias,
The occupation factor is regular.. (i.e. every unit cell there is 0.5 of a particular magnetic site!)
Regards,
Vassilis
-----Original Message----- From: comp-phys-alps-users-bounces@phys.ethz.ch [mailto:comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer Sent: Sunday, April 05, 2009 11:49 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] Occupation factor
Dear Vassilis,
is this occupation of 0.5 regular, in a pattern, or random?
Matthias
On Apr 5, 2009, at 10:03 AM, Vassilis Tangoulis wrote:
Dear Users,
Consider a system with different magnetic sites but the crystallographic occupation factor of some of them is less than 1.0 (lets say 0.5). How can we describe this in the lattices.xml file where we develop the unitcell?
Kind regards,
Vassilis
Vassilis Tangoulis Lecturer in Inorganic Chemistry Laboratory of Inorganic Chemistry, Department of Chemistry Aristotle University of Thessaloniki, 54124 Thessaloniki,GREECE Tel : +30 2310 997 676 Fax : +30 2310 997 738 Email: vtagkoul@chem.auth.gr =================================================================
There are systems with formulas of the type MxNy where the x, y can take values non integer. In my case I have a Ni3Cr4.5 system where there is repeating unit forming a 1D chain of the type Ni3Cr3 while in every such unit there is a extra Cr ion (forming no bonds with this unit) with occupancy half (in crystallography this is the way to characterize sites that do not belong entirely to one unit cell).
Hope I made myself clear
-----Original Message----- From: comp-phys-alps-users-bounces@phys.ethz.ch [mailto:comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer Sent: Monday, April 06, 2009 6:28 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] Occupation factor
What do you mean by 0.5? how can you have half a site?
On 5 Apr 2009, at 20:03, Vassilis Tangoulis wrote:
Dear Matthias,
The occupation factor is regular.. (i.e. every unit cell there is 0.5 of a particular magnetic site!)
Regards,
Vassilis
-----Original Message----- From: comp-phys-alps-users-bounces@phys.ethz.ch [mailto:comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer Sent: Sunday, April 05, 2009 11:49 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] Occupation factor
Dear Vassilis,
is this occupation of 0.5 regular, in a pattern, or random?
Matthias
On Apr 5, 2009, at 10:03 AM, Vassilis Tangoulis wrote:
Dear Users,
Consider a system with different magnetic sites but the crystallographic occupation factor of some of them is less than 1.0 (lets say 0.5). How can we describe this in the lattices.xml file where we develop the unitcell?
Kind regards,
Vassilis
Vassilis Tangoulis Lecturer in Inorganic Chemistry Laboratory of Inorganic Chemistry, Department of Chemistry Aristotle University of Thessaloniki, 54124 Thessaloniki,GREECE Tel : +30 2310 997 676 Fax : +30 2310 997 738 Email: vtagkoul@chem.auth.gr =================================================================
Then actually the real unit cell is twice the size
On 5 Apr 2009, at 20:39, Vassilis Tangoulis wrote:
There are systems with formulas of the type MxNy where the x, y can take values non integer. In my case I have a Ni3Cr4.5 system where there is repeating unit forming a 1D chain of the type Ni3Cr3 while in every such unit there is a extra Cr ion (forming no bonds with this unit) with occupancy half (in crystallography this is the way to characterize sites that do not belong entirely to one unit cell).
Hope I made myself clear
-----Original Message----- From: comp-phys-alps-users-bounces@phys.ethz.ch [mailto:comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer Sent: Monday, April 06, 2009 6:28 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] Occupation factor
What do you mean by 0.5? how can you have half a site?
On 5 Apr 2009, at 20:03, Vassilis Tangoulis wrote:
Dear Matthias,
The occupation factor is regular.. (i.e. every unit cell there is 0.5 of a particular magnetic site!)
Regards,
Vassilis
-----Original Message----- From: comp-phys-alps-users-bounces@phys.ethz.ch [mailto:comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer Sent: Sunday, April 05, 2009 11:49 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] Occupation factor
Dear Vassilis,
is this occupation of 0.5 regular, in a pattern, or random?
Matthias
On Apr 5, 2009, at 10:03 AM, Vassilis Tangoulis wrote:
Dear Users,
Consider a system with different magnetic sites but the crystallographic occupation factor of some of them is less than 1.0 (lets say 0.5). How can we describe this in the lattices.xml file where we develop the unitcell?
Kind regards,
Vassilis
Vassilis Tangoulis Lecturer in Inorganic Chemistry Laboratory of Inorganic Chemistry, Department of Chemistry Aristotle University of Thessaloniki, 54124 Thessaloniki,GREECE Tel : +30 2310 997 676 Fax : +30 2310 997 738 Email: vtagkoul@chem.auth.gr =================================================================
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