Hi,
On 06 Aug 2014, at 11:55, D´Souza, Sunil Wilfred sunilwilfred@cpfs.mpg.de wrote:
Dear ALPS users, I am just a beginner in the ALPS simulations.The description of my question is as follows:
As a practice exercise, I want to run the quantum montecarlo simulations using the spin ½ model defined in the ALPS library to calculate the Curie temperature (Tc) of bulk Iron metal by considering the BCC structure with a = 286.65 pm. Therefore, I have generated a BCC structure with first and second nearest neighbors. I have attached the structure related xml file “Fe.xml” along with this mail for your consideration. Firstly, It is well known that the BCC structure has 8 first nearest neighbors placed at ( ±½, ±½, ±½ ) positions with respect to the vertex at (0, 0, 0). In the xml file I have defined only two nearest neighbor edges connecting the (0, 0, 0) to (½, ½, ½ ) and (-½, ½, ½ )positions in the unit cell. Thereafter, when i viewed the structure by using lattice-preview program in the periodic boundary condition with L=2,it is showing all 8 nearest neighbors. My question is that due to the definition of periodicity does the simulation takes into account all 8 nearest neighbors even though if I don't define the 6 other nearest neighbors explicitly in the unit cell.
If you read the tutorial you will see that the offsets are integers, referring to the unit cells, and not the coordinates. You can take a look at the ALPS "body-centered cubic lattice", or just use that one if it fits.
Secondly, along with the above mentioned issue on the definition of the structure, I am kindly requesting you to provide me some insights regarding how to calculate the Curie temperature of Iron metal by using the ALPS simulation in terms of which programs I have to use in order to accomplish this task. A simple example describing this task would be of very great help.
You will have to write down the model that you want to solve, e.g. a Heisenberg spin model with the appropriate parameters. Please note that ALPS is not an ab-initio program, but a program for solving effective models.
Matthias Troyer