Orthorhombic Structure Calculation

[Tim Hackett]

Greetings Vampire Users,

I am working with Fe2AlB2 which is a well studied orthorhombic (Cmmm, space group no. 65) system.  The lattice constants are x = 0.2923 nm, y = 1.1046 nm, z = 0.2875 (ref SpringerMaterials).  Well, after reading through the mailing list, reading the manual, and playing with the .ucf file, I was unable to find the best way to run an orthorhombic system to acquire a Curie Temperature (lit. value of 329 K).  I am also a new user of Vampire (v. 4.0) and I am running Ubuntu (v. 16.04) on an Omen by HP gaming laptop.  My question: is there an add on package or goodies software that will allow me to run an orthorhombic crystal structure?  Thank you for addressing my post.

[Richard Evans]

Dear Tim,

The orthorhombic system can be run in VAMPIRE as long as you do not use the truncation facilities such as particle shapes, layers etc - ie a bulk-like system with or without periodic boundaries (we did this for some simulations of ZnO). The problem here is the parallelization which forces cubic cells, and so to fix this I need to implement a dual coordinate representation so that the parallelization is done as usual assuming unit cell coordinates, while the truncation routines are applied to the orthorhombic cell.

Also I would recommend running the latest develop branch of the code as there are many new features. We are hoping to update the manuals and tutorials for an official release in the summer.

All the best,

Richard

On 25 Apr 2018, at 21:57, Tim Hackett <thacke...@gmail.com> wrote:

Greetings Vampire Users,

I am working with Fe2AlB2 which is a well studied orthorhombic (Cmmm, space group no. 65) system.  The lattice constants are x = 0.2923 nm, y = 1.1046 nm, z = 0.2875 (ref SpringerMaterials).  Well, after reading through the mailing list, reading the manual, and playing with the .ucf file, I was unable to find the best way to run an orthorhombic system to acquire a Curie Temperature (lit. value of 329 K).  I am also a new user of Vampire (v. 4.0) and I am running Ubuntu (v. 16.04) on an Omen by HP gaming laptop.  My question: is there an add on package or goodies software that will allow me to run an orthorhombic crystal structure?  Thank you for addressing my post.

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[Federico Brivio]

Dear Richard and Tim.

I am in a similar Situation. After a reading of the workshop materials, I do have an idea about how to run a basic simulation, but some points are obscure.

1) In the workshop some passages are unclear: e.g. "Calculate exchange by looping through each atom in the central cell, looping again through all other atoms - if neighbour is within range, call exchange function to calculate energy" Is there a program we should use, or is something done inside vampire?

2) Both the Atoms num and Interaction in the unit cell file have some unclear tags: lc, hc, exctype. What are they supposed to mean?

3) Building the interactions tensor: are we supposed to assign Next Neighbour atoms in a super-cell expansion?

I think I am missing some pieces of information and I am concern to fill the void with not-proper assumptions.

As reference, I am working on a magnetic mof (at the DFT level), and we are calculating the J_{ij} parameter for each possible interaction within the single cell.

Cheers,

F.

[Jiahao Chen]

Dear Richard,

Good to hear that orthorhombic system can be run on Vampire. I don't quite get the details of truncation faciillites you mentioned, but could you give an explicit hint of which part should be cautious in input file or material file ?   By the way, I am working on the Fe2O3 system which is trigonal unit cell, but I double the trigonal cell into orthorhombic unit cell, it that alright to run the code ?

Best regards,

Jiahao Chen

在 2018年4月26日星期四 UTC+1上午10:02:03，Richard Evans写道：

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