DMFTLab Library Documentation

 

 

Table of Content

 

1. Overview of DMFTLab. 2

2. Setting the Data: Overview.. 3

3. Computing Properties: Overview.. 6

4. Using DataBase: Overview.. 8

5. LmtART program.. 9

A.1 Computing Spectral Functions at Imaginary Axis. 10

A.2 Computing Spectral Functions at Real Axis. 10

B.1 Visualizing Spectral Functions at Imaginary Axis. 11

B.2 Visualizing Spectral Functions at Real Axis. 12

C.1 Accessing General Properties. 13

C.2 Accessing Interactions Properties. 14

C.3 Accessing Grids. 15

D.1 Setting General Properties for a Level 16

E.1 Accessing Method Convergency Options. 17

E.2 Accessing Method Mixings Options. 18

F.1 Accessing Method Settings. 19

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

© Copyright 2005 University of California Davis

1. Overview of DMFTLab

 

Welcome to DMFTLab, the scientific software for Windows systems that performs calculations of properties of several most popular versions of model hamiltonians. DMFTLab is a library dynamically linked to MStudio. DMFTLab also uses MScene library for visualization.

 

 

DMFTLab consists of a window that is used to set up input data, perform calculations and analyze output data. The DMFTLab Window, shortly DMFT Window is called using DmftLab command of the Project menu or corresponding button of the DMFTLab Toolbar.  The DMFT window consists of two Property Pages:

  • Setup Pagedmflab_setup_overview
  • Properties Pagedmftlab_properties_overview

 

A lower area of the DMFT Window is an output area where the output of the calculation is shown.

 

The engine of the DMFTLab is a program called LmtART.dmftlab_lmtart_overview The LmtART is an executable file that reads the input data, performs calculation, and stores the output files. The DMFT Window only controls this process, it prepares input for the LmtART using dialog windows, and starts LmtART program as a separate thread. When the calculation is finished, LmtART notifies the DMFTLab, and the output files are read by the DMFT Window and can be visualized by simple mouse click operations.

 

While running LmtART program for complicated setups can be rather slow, the DMFTLab can be used to prepare the input files, after which they can be copied to another computer where the LmtART can be run in a faster way. After run is performed, the output files can be copied back to the PC and DMFTLab can analyze them quickly. All input/output files are formatted, and therefore system independent.

 

The DMFTLab uses scratch directory to run LmtART program. By default scratch directory is called LmtRUN. It exists at the MStudio installation directory. All input/output files prepared by the DMFT window are stored in this directory.

 

A separate issue of the DMFTLab is its Database. The DMFTLab has a database of various setups that have been calculated using the LmtART program. The database is an important part of the library, it can be called by pressing DataBase button located on the top right part of the DMFT Window. The input/output files can be stored within the database: this gives possibility to use these files on the remote machines. Refer to Using DataBasedmftlab_database_overview topic for the detailed discussion.

2. Setting DMFT Data: Overview

 

The first property page of the DMFT Window is designed to describe model hamiltonian parameters:

 

  • Temperature or reciprocal temperature
  • Model hamiltonian choice
  • Intraatomic Coulomb interaction parameters U and J
  • Imaginary axis grid settings
  • Real axis grid setting

 

More options can be accessed via clicking Access All Options button. The corresponding property pages are

 

  • General PropertiesHIDD_ALLOPTIONS_GENERAL
  • Interactions PropertiesHIDD_ALLOPTIONS_INTERACTIONS
  • Grids PropertiesHIDD_ALLOPTIONS_GRIDS

 

 

 

The following set of data has to be given for each impurity level

  • Level title, like “s-level”, “p-level”. If spin polarization is desired, specify in the title either “-up”, or “-dn” keyword.
  • Energy of the impurity level. Note that the energy has to be set with respect to particle hole-symmetry point, i.e. it is doping position. If bare position of impurity level is Ef, the doping position is Ef-U(N-1)/2, where U is Hubbard U parameter set up above.
  • Degeneracy of the level.
  • Quarter of bandwidth. For the Hubbard model this is quarter of bandwidth of the band. For the periodic Anderson model, this is the quarter of bandwidth of conduction band.
  • Conduction band position. This option is only necessary for the periodic Anderson model.
  • Hybridization between the conduction band and impurity level. This option is only necessary for the periodic Anderson model.

 

Additional options for atoms can be accessed by highlighting the entire row and calling the Properties dialog box with the right mouse button.

 

 

 

Another possibility to call the Level Properties dialog box is to access it from the Object Explorer.

 

 

 

The dialog box which allows to access various properties for the selected level appears. These properties include:

 

  • General PropertiesHIDD_SETLEVEL_GENERAL

 

 

3. Computing Properties: Overview

 

Computation of properties of model hamiltonians is the goal of the DMFTLab library. The LmtARTdmftlab_lmtart_overview program is the executable module that does this calculation. It reads input files prepared by the DMFT Window, performs the calculation of the desired property, and notifies the DMFT Window again that the calculation is finished. The DMFTLab reads the output files and visualizes them with help of the MScene library.

 

 

The purpose of the Properties page of the DMFT Window is to make final preparations before starting LmtART, start LmtART code, and visualize the output data computed by the LmtART. Once the data are set using Setupdmftlab_setup_overview property page, the last step is to choose the method of computing the physical property.

 

Several methods are currently available within the use of DMFTLab library:

 

  • Hubbard I method
  • Slave-boson mean field method.
  • Rational Interpolation method

 

Each method has its own set of options which can be set by clicking Settings. A set of options to perform self-consistency can be accessed via clicking SCF Options button. It includes

 

  • Convergence criteriaHIDD_DMFT_CONV
  • Mixing optionsHIDD_DMFT_MIXING

All methods perform DMFT self-consistent calculation to find spectral functions at imaginary axis. To make self-consistency, switch on radio button Make Self-Consistency and click Compute button. The self-consistent calculation will start. The output window in the lower part of the DMFT Window will show haw the self-consistent process is performed. This however maybe rather slow process. At the end of the calculation, the framework creates the file consisting the self-consisting spectral functions data.

 

Once self-consistency is performed, physical properties can be computed.

 

To compute physical property such as Spectral Functions in Real Axis, set radio button Find Property to the On position.  Chose the property from the drop-down list and press Compute button. ( You may also use Prepare button to set more options before pressing compute button.) 

 

The following set of properties can be computed by the DMFTLab:

 

  • Spectral Functions at Imaginary AxisHIDD_COMPUTE_IMW
  • Spectral Functions at Real AxisHIDD_COMPUTE_REW

 

After the computation of a particular property is finished, the framework will add this into the computed properties list of the Visualize Property drop-down list.

 

To start visualizing the properties that have been computed, choose radio button Visualize Property. Highlight corresponding property and press Visualize button. A visualization dialog box appears. You can start visualizing the data by pressing Visualize with the current settings button in the lower part of this dialog box.

 

The following controls help to visualize the computed properties:

 

  • Visualzing Spectral Functions at Imaginary AxisHIDD_VISUALIZE_IMW
  • Visualizing Spectral Functions at Real AxisHIDD_VISUALIZE_REW

 

All visualization plots can be additionally customized using the commands of MScene library. Refer to the MScene Library documentation for corresponding instructions.

4. Using DMFT DataBase: Overview

 

The integrated database is important part of the DMFTLab library. Instead of maintaining its own input files, one can use database to extract set-ups for similar problems and then slightly modify them.  After computation of the properties and or self-consistency process is performed one can store the computed data into the database to be able to use them in the future runs.

 

 

To call database press Database button located at the top right part of the DMFT window. The database dialog box appears. The database consists of catalogs and their contents. A set of predefined catalogs describing set-ups for some simple models is provided with this installation.

 

To load data from the database into the DMFT Window select a particular model and press Load Data button. To store data computed by the DMFT Window, use button Add to Catalog located on the top of the database dialog box.

 

New catalogs can be created and removed. Entries within the catalog can also be removed using corresponding buttons.

 

In fact, the database maintained by the framework is located in the database folder of the directory where installation of MStudio has been performed. Navigate database folder, the input and output files for many different examples are stored in its subdirectories. All these files are either input or output files of the LmtARTdmftlab_lmtart_overview program that performs actual computations. Refer to the LmtART manual for detailed instructions about input and output to this program.

5. LmtART program

 

LmtART is free scientific software designed to perform electronic structure calculations of the materials. It is written using Fortran 90 programming language and uses full dynamical memory model. The source codes for that program, as well as installation and operating instructions can be downloaded from the same site as the MStudio, MScene, BandLab, and DMFTLab libraries. Refer to specific license agreement and copyright notice when using LmtART codes.

A.1 Computing Spectral Functions at Imaginary Axis

 

To compute density spectral functions at imaginary axis, the self-consistent DMFT loop is used. The paramters of self-consistent cycle can be chosen.

 

 

A.2 Computing Spectral Functions at Real Axis

 

To compute density spectral functions at real axis, the self-consistent DMFT loop is used. The parameters of self-consistent cycle can be chosen.

 

 

 

B.1 Visualizing Spectral Functions at Imaginary Axis

 

In order to visualize spectral functions, use Visualize Spectral Functions dialog box. Enter lower and upper frequency limits. For crystal filed case or spin polarized case you may setup which representation and spin to visualize. If representation and/or spin is set to zero, a sum over all representations and/or spins will be performed. This makes sense for such properties as the Density of States only.

 

A special tree control exists to set up which spectral functions should be drawn. Drag them from the Property folder and drop them within the Page folder into the icon showing the Page. Note that you can use right mouse button to access to the pop-up menu with Rename, Delete, Add commands. You can add new Pages and drag calculated properties to every of these pages.  In this way, you can set up spontaneously several pages with each page containing several graphs. When you are done with the descriptions of graphs, press Visualize button at the button. The program will use the graphical library to draw selected set of properties.

 

B.2 Visualizing Spectral Functions at Real Axis

 

In order to visualize spectral functions, use Visualize Spectral Functions dialog box. Enter lower and upper frequency limits. For crystal filed case or spin polarized case you may setup which representation and spin to visualize. If representation and/or spin is set to zero, a sum over all representations and/or spins will be performed. This makes sense for such properties as the Density of States only.

 

A special tree control exists to set up which spectral functions should be drawn. Drag them from the Property folder and drop them within the Page folder into the icon showing the Page. Note that you can use right mouse button to access to the pop-up menu with Rename, Delete, Add commands. You can add new Pages and drag calculated properties to every of these pages.  In this way, you can set up spontaneously several pages with each page containing several graphs. When you are done with the descriptions of graphs, press Visualize button at the button. The program will use the graphical library to draw selected set of properties.

 

 

C.1 Accessing General Properties

 

Describe general properties such as model hamiltonian choice, temperature and the shape of non-interacting density of states.

 

C.2 Accessing Interactions Properties

 

Intraatomic Coulomb interaction parameters, Hibbard U and exchange J are set using this property page.

 

Their evaluations can be done using Slater integrals by selecting the corresponding l shell of the atom.

 

 

C.3 Accessing Grids

 

Imaginary axis (Matsubara grid) settings are described by a number of points and the temperature. Logarithmic grid is used to accelerate the calculation. It is set by the number of points and the effective bandwidth. The cutoff frequency will be evaluated automatically from these settings

 

 

To compute the spectral functions at real axis, specify minimal and maximal frequency as well as the number of points.

 

 

D.1 Setting Properties for a Level

 

Description of the correlated level.

  • Level title, like “s-level”, “p-level”. If spin polarization is desired, specify in the title either “-up”, or “-dn” keyword.
  • Energy of the impurity level. Note that the energy has to be set with respect to particle hole-symmetry point, i.e. it is doping position. If bare position of impurity level is Ef, the doping position is Ef-U(N-1)/2, where U is Hubbard U parameter set up above.
  • Degeneracy of the level.
  • Quarter of bandwidth. For the Hubbard model this is quarter of bandwidth of the band. For the periodic Anderson model, this is the quarter of bandwidth of conduction band.
  • Conduction band position. This option is only necessary for the periodic Anderson model.
  • Hybridization between the conduction band and impurity level. This option is only necessary for the periodic Anderson model.

 

E.1 Accessing Method Convergency Options

 

Settings for DMFT self-consistency loops both at imaginary and real axis can be specified as well as convergency criterium.

 

E.2 Accessing Method Mixings Options

 

Mixing options for both Broyden and linear mixing schemes can be specified including the choice of mixing function.

 

 

F.1 Accessing Method Settings

 

Each method has its own set of additional options. For fully degenerate model select SU(N) symetry case. For levels split by crystal fields, select crystal field splitted case.