Input Wizard ; Set up 'lapwin' file.

Click Input Wizard. $\Rightarrow$General Structure Window will appear.

2.3.1

PULL DOWN MENU
There are four pull-down menus, which are, File, Import, Help, and Visualize.

• File; user can read from the 'lapwin' file in current directory, or start from scratch (See (NOTE) at the end of this section on page 10). Also there is save 'lapwin', or exit.
• Import; to import from the XTL input, click Import XTL file. The Import Structure window appears. Enter the directory from where you want to get the XTL input files or click on Go to Examples, and click Filter *.xtl files button. A list of all XTL files in the given directory will appear in the window on the left. Choose among the *.xtl files from the list and click Import. GUI will automatically figure out the lattice vectors and atomic positions (in internal coordinates). Click Done to finish. Skip steps (B), (C), (D), (E), (F), (H), (I), (J) and (K) in '2.3.2 TYPE-IN INPUTS'.
  User also can import/export 'lapwin' file from/to the archive. For this, click Import/Export from FLAPW input archive. The Import/Export to Archive window will appear. It will automatically find the Archive directory of GUI. Change the directory if necessary. To import a 'lapwin' file from the archive, double click one of the files appearing on the left window. The file will be imported with the small window disappeared. To export the 'lapwin' file, enter the file name and click Save to archive. Click Done when finished.

• Help; get connected to the 'web elements' web site, the FLAPW Users Guide or README file for GUI.

• Visualize; visualize your system using RasMol. After entering the atomic information ((A)-(Q) in '2.3.2 TYPE-IN INPUTS'), click Visualize $\rightarrow$ using RasMol. The Visualize Structure Window will appear. Clicking Show me!, the RasMol Window will appear. The size of the atoms are proportional to their Rmt (See 2.3.2 (O)(a)) - make sure that the Muffin-tins are not overlapping. Move the mouse to rotate the figure. You may choose Bounding Box or Show axes on Visualize Structure Window. Click Done to finish. If the Show me! button doesn't show the RasMol window, please check your configuration for RasMol (see Section 2.1.). Check the

  RasMol directory shown in the GUI Configuration and try other RasMol options that are good for your machine.

2.3.2

TYPE-IN INPUTS ON THE General structure WINDOW;

(A)

Type in Job Title.

(B)

Click FLAPW input format to choose either FLAPW or Alternative input format. Watch the message appearing in the box above the Lattice parameters input. The FLAPW format lets the user input a scaling parameter and the lattice vectors, while choosing the Alternative format the user can enter the lattice parameters (a, b, and c), and the Angles. Item (F) below will depend on your choice made here.

(C)

Click Bulk Mode to choose either Bulk or Film.
(Note) When 'lapwin' is read from an existing file, items (B) and (C) are not changeable.

(D)

Click Use INTERNAL coordinates to choose the coordinates of atomic positions input (see (I)) ; either INTERNAL or CARTESIAN.

(E)

Click in Bohr to choose units of the Lattice Parameters which you will input in (F) and (G) below; either in Bohr or in Angstroms.

(F)

Click Plane Lattice (for Film Mode) or Space Lattice(for Bulk Mode) to choose the lattice from the pull-down menu. GUI will automatically set your Angles and Lattice Vectors. Or you can enter them directly by typing them in.
Enter the Lattice Parameters. For FLAPW input format (see (B) above), you need to enter the scaling factor, a, while for Alternative input format you can enter a, b, c, and Angles separately. The lattice parameter can be adjusted by either V/V_o or T/T₀. After entering the lattice parameters, enter a desired ratio of V/V_o or T/T₀ and click the Scale Lat. Par. button. The lattice parameter will be recalculated accordingly. The tetragonal distortion, T/T₀, can be calculated either keeping the volume constant or not by clicking the V=const button. If V=const is chosen, the c/a ratio as well as the in-plane lattice a and b will be scaled so that the volume is conserved. If V=const is not chosen, the in-plane lattice a and b will be fixed but only c/a ratio will be changed.

(G)

For Film Mode, enter the film thickness, D and D' in the units that you choose in (E) above.

(H)

Now for the atomic inputs, click Choose element from Periodic Table. Click on atom you want to add from the Periodic Table of Elements. Check if it appears in the Current atom is: box in the General Structure Window. Click Close of the Periodic Table window to close. Or you can type in directly the atomic name in the Current atom is: box.

(I)

Enter the atomic positions into the three (two for Film Mode) boxes below With the coordinates (x,y,z) in the appropriate coordinates you've chosen in (D). Click Add to add the current atom in your input file. The atom will appear in the blue Atoms in the unit cell window on the left. Repeat (H) and (I) to add as many atoms as you want.

(J)

To add equivalent atoms, choose an atom from the Atoms in the unit cell window by clicking on it, enter atomic positions, and click Add equivalent. The atomic name of the equivalent atom will appear as *.

(K)

To edit any of the atomic positions listed in the Atoms in the unit cell window, click on the atom in the window, make sure the atom you want is highlighted, make change, and click Edit. To delete, click on the atom to choose and click Delete.

(L)

Click Fix Symmetry. This will find the equivalent atoms and the symmetry of the system. Click OK on the pop-up message saying Atoms in the unit cell symmetrized.... The FLAPW will find the symmetry operations and re-write the atomic inputs in the 'lapwin' file. The result will be shown in the left box of the atomic inputs.

In case your inputs for atoms in the unit cell does not correspoind to a primative cell there will be a message saying so. You might click Fix manually to check out the input yourself or click Fix primitive cell to let GUI try to figure out the primitive cell from your input. Upon choosing Fix primitive cell, make sure that the re-generated unit cell shown in the blue window is correct.

(M)

Click k-point Settings. The Set up k-sampling options Window will appear.

(a)

In order to use the pre-defined k-points, prepare 'spkpt.init' file and click on Use spkpt.init file on top. Then FLAPW will look for the 'spkpt.init' file in the working directory and use the k-points listed in that file, neglecting item (c) below.

(b)

Click the next two boxes if desired:

• Use the Time-reversal Symmetry.

• Use Gaussian smearing. Upon choosing this feature, make changes for the Gaussian Smearing (in Hartree), if desired. If Gaussian smearing is not chosen, FLAPW will use the tetrahedron method for integration as the default. For Gaussian, if desired, make changes for the Gaussian Smearing.

(c)

Enter the valence (and the semicore for Double Window calculation) window k-point divisions in the x, y, and z directions. By clicking Suggest minimal uniform k-mesh button, one can start from the minimal uniform k-mesh, which is determined according to the different lengths of lattice vectors. If required, it is recommended to increase the k-mesh and maintain similar proportions of the minimal k-mesh to keep it as uniform as possible. By choosing odd numbers for the k-points division, the user can include the high symmetry point ($\Gamma$). There are three buttons, (i) x2; doubles the divisions along each axis, (ii) x3; triples the divisions along each axis (iii) Odd; makes the number of divisions an odd number. Also enter the semi-core window k-point division for the Double Window calculation.

(d)

click Done.

(N)

Click General Options to select the type of calculation

desired from various features of the FLAPW code. The General Options window will appear. Click on the small box in front of each item to choose. Depending on the item, the Options button will be activated. Click the button to generate the required input files for each feature.

(a)

Click Spin-polarized regime for the magnetic system.

(b)

Click Double Window calculation to include semicore states.

(c)

Click Generalized Gradient Approximation for GGA. The default is LDA.

(d)

Clicking on Geometry optimization, the Geometry Optimization Setup window will appear which generates the 'inputopt.dat' file in the current directory.

• Click Use Broyden method to choose either Broyden or Newton method. For Broyden, enter mixing parameter (real number between 0.0 and 1.0). If desired, change the convergence criterion for the force, from the default value, 0.002 (Htr/a.u.). Geometry optimization will consider the forces to be practically zero when they are less than this value.

• Click to choose an atom in the large blue window. The atom will appear in the boxes below the blue window. Click x=Move box to choose either Move (to optimize) or Fix (to fix) the X coordinate of the current atom. Also do the same for Y and Z. For the coordinate to Move, enter the maximum shift allowed in each optimization step, in the box dx, etc. For Newton method, also enter the damping factors in each direction for each atom. Click Accept changes. Continue for the next atom.

• Click Quit and Save to go back to General Options window. The 'inputopt.dat' file will be generated in the working directory.

(d)

Click the Force or Frequency calculation box if desired.

(e)

Clicking on Screened Exchange and Options, the SX/Model GW Setup window will appear which generates the 'inputsx.dat' file in working directory.

• Click either Model GW or SX-LDA to choose the method.

• Choose either All valence electrons or Enter a number below to decide the electrons in the screening. For the latter, enter the number of electrons to put in the screening in the box.

• Enter the G Cut-off and Lmax.

• For the Model GW approach, input the dielectric constant.

• Click Done to go back to General Options Window.

(f)

Click on Calculate spin-orbit interaction to include the spin-orbit effect in the calculation. If desired, click Calculate SO self-consistently. Default is the second variational one-shot calculation for spin-orbit interaction.

(g)

To calculate the p-matrix (for SMOKE or Optics), click on Calculate P-matrix(for SMOKE). For SMOKE, make sure that your have spin-polarized system with the spin-orbit interaction calculation (Choose T in item (f) above). For the optical properties calculation, you may choose the longitudinal form. Use Properties menu for the optical properties calculation (See 2.5.4. below).

(h)

To calculate the L-matrix for MCD, click on Calculate L-matrix(for MCD). We recommend the user to do MCD from the Properties menu (See 2.5.5 below) which will guide the user generating an input file required for MCD calculations.
For SMOKE, MCA, and MCD calculations, make sure that you have a converged charge density in the working directory. FLAPW will generate the data files of p-matrix or l-matrix, which can be used by an external module to obtain SMOKE, MCA, and MCD results.

(i)

If desired, click to choose Use second variational for non-MT potential.

Click Done to go back to General Structure window.

(O)

Click LAPW parameters. The Runtime LAPW parameters Window will appear. On this window;

(a)

Enter the atomic information for the Valence window (and for the Semicore window for the Double Window calculation (See (M)(b) above). The blue box on top lists the atomic information, including the atomic species, default values of Rmt (Muffin-tin sphere radius), Ncore (number of core states), M (initial atomic magnetic moment for the spin-polarized system), Lmt, Lmax, and the number of radial points, and the energy parameters shifts (Enu) of s, p, d, and f states for each atom type will be automatically estimated by the code if the default values, which are set equal to zero, are chosen.
The default values of Rmt are set to 2.0 (a.u.) for most of the atoms. (These are holding place values.) You will need to change them to proper values depending on your system. To change the Rmt or Ncore from the default value, (i) click to choose the Valence window, (ii) click on the atom from the blue box, (iii) make changes of Rmt and Ncore in the small boxes above the blue box, then (iv) click Make changes at the bottom. See if the atomic information in the blue box shows the change. To change other atomic information besides Rmt or Ncore, see item (e) below.

(b)

In case you have a Double Window calculation, to set up the Semicore states, click Semicore window, click on the atom from the blue box, and choose the Semicore states by clicking on the proper box on the right hand side. See if the Ncore for the atom and the Number of states to calculate at the bottom change correctly according to your input.

(c)

For the spin-polarized system, enter the initial atomic spin magnetic moments, by either global or individual initial atomic moments. Upon choosing Set individual initial ..., click each atom on the blue window to choose, enter the initial magnetic moment for each atom, one by one, and then click Make changes. See if the M value in the blue box reflects your change correctly. Or, for Set global initial..., enter the initial magnetic moment which will be given to all atoms and then click Make changes.

(d)

Each time the Rmt values are changed, the cut-off parameters and the number of states are automatically updated. If you don't want this feature, click to unmark the Auto-estimate cut-off parameters. Then the auto-estimation will be done only when the 'Estimate' button is clicked (See item (e) below).

(e)

In order to change more atomic information and the cut-off values,

click Enable Advanced parameters.

• Choose the Valence window (or Semicore window on the top for the Double window calculation).

• To change advanced atomic inputs, (i) click on the atom from the blue box, (ii) make changes on Lmt, Nrad, Lmax (for Valence window only) or the energy parameters shifts (Enu) for each state (for both Valence and Semicore windows). As stated above, the energy parameters will be automatically estimated by the code if the default values, which are zero, are chosen. To change the energy parameter from the default value, enter the desired value in the box below the proper state at Energy shifts for automatic Enu's (optional) box. Then the energy parameters will be lifted by the entered value from the estimated ones.

• Number of states and the cut-off values; if desired, change them from the default values. Since each 'state' is occupied by two electrons, the number of states may be an integer which is larger than half the number of valence electrons. For Semicore window, the number of states is determined by your choice of Semicore states given in item (b) above and therefore only the PW cut-off may be changed. Or you can let the GUI estimate the proper values for your system, by clicking 'Estimate' button.

• Core setting; if you want to use non-standard core settings, click Non-standard settings for core. Then, the View/edit set_core.init button will be activated. Clicking on that button, the editor will show the 'set_core.init' file so that the user can make changes by hand. (Make sure that you have set the editor as indicated in item 1.3 upon the installation of GUI.) The 'set_core.init' file includes the core settings information as follows: for each atom, a number on the first line shows the number of core states. Then, there follow lines with four numbers which are l, K, the number of majority electrons, and the number of minority electrons, respectively, for each core state. Make changes, save and quit by hand. Change the Ncore (See item (a) above) according to your core setting.

• Background charge; if desired, enter the background charge (positive for electrons and negative for holes).

(Note)

• Once you make changes in the atomic information, the GUI database will be updated by the new values. If you want to restore the original atomic information, go to the GUI Configuration (See section 2.1 above) and click Reset to default values button.

(f)

To finish and go back to General Structure Window, click Make changes and Done.

(P)

Click Mixing scheme. Make changes on the mixing for charge density, maximum number of iterations, and the convergence criterion. For the spin-polarized system, choose the mixing scheme and parameter for the spin density, too. The linear spin density mixing is the default. Also determine whether you want to treat the Spin Up and Down in one vector. Click Done to finish.

(Q)

Click Generate Supercell to generate the supercell. Supercell Generation window will appear. Enter how many times you want to repeat the unit cell along each unit cell vector. Click Generate and Done to finish.

(R)

Click Check MT overlap to check if the muffin-tins are overlapping. If you get the message saying 'Atoms overlap', go back to LAPW parameters and fix the Rmt (See item (O)(a) above).

(R)

To finish, click either Save LAPWIN, Quit without changes to LAPWIN or Generate new LAPWIN and Quit to finish. Generate new LAPWIN and Quit will generate a 'lapwin' file in your working directory (and the input files generated in the General Options).

(NOTE)

1. If you have a 'lapwin' file in your current directory where you run the GUI, the GUI will replace this 'lapwin' (ie., overwrite it). Your previous 'lapwin' will be automatically copied to 'lapwin.bak' file. In order to generate a 'lapwin' file from scratch, choose General structure window $\Rightarrow$File (pull-down menu) $\Rightarrow$ Reset all without re-reading.

2. This guide is for the GUI. For general questions about the meaning of each input variable in a FLAPW calculation, click General structure window $\Rightarrow$Help (pull-down menu) $\Rightarrow$ FLAPW User Guide.