DFT + Hubbard U, PDOS
*********************

BAND DFT+U Hubbard-U Band gap pDOS

This tutorial will show you how to perform a single point calculation
with the DFT+U formalism using the BAND engine.


Step 1: amsinput
================

   **1.** Start AMSinput
   **2.** Switch to **BAND**: [image: ADFPanel][image] **→** [image: BANDPanel][image]
 [image]


Step 2: Setup the system - NiO
==============================

You can copy-paste the following information into the AMSinput
directly.

   2

   Ni    0.000  0.000  0.000
   O     2.085  2.085  2.085
   VEC1  0.000  2.085  2.085
   VEC2  2.085  0.000  2.085
   VEC3  2.085  2.085  0.000

By default, only the central unit cell is shown. To see a few unit-
cell repetitions:

   **1.** Click on **View → Periodic → Periodic View Type → Repeat Unit Cell**
   **2.** Use the mouse to rotate (left mouse button) and translate (right mouse button) the crystal to your favorite orientation.

Note:

  If needed. To repeat the unit cell in each direction, choose the
  range "[-1,1]". Click on **View → Periodic → Unit Cell Range...**.
  In the first cell of the pop-up window, enter 1. The other cells
  will automatically update with the proper range.

[image]


Step 3: BP86 without Hubbard
============================

Change the calculation setup (Unrestricted, XC functional, basis set)
as follows:

   1. Check the **Unrestricted** box.
   2. Set **XC functional** to **GGA:BP86**.
   3. Set **Basis Set** to **TZP**
   4. Tick the checkbox **PDOS**
 [image]


Step 3a: Run the calculation
----------------------------

Now you can save and run the calculation.

   **File → Save**, give it a name and press Save.
   **File → Run**

Note:

  AMSjobs should come to the foreground, and your job should be
  visible at the top. On the right side you can see that the job is
  running (this is indicated by the gear-icon). When running, in the
  AMSjobs window the progress of your simulation is showing (from the
  logfile).


Step 3b: Checking the results
-----------------------------

After the calculation finished, you can check the Output for the 'Band
Gap Info'.

   **SCM → Output**
   **Properties → Band Gap Info**

One can see that there is no band gap at all. This contradicts
experimental studies, which predict values between 3.7 to 4.3 eV.

[image]

Plotting and examining the partial density of states (pDOS) for this
calculation reveals that the d-orbital contributions of Ni are
crossing the Fermi level.

   **SCM → DOS**
   In the system viewer on the left, select a **Ni atom**
   Choose **Partial → Ni(1) → d-DOS**
   Double click on the Energy axis and change:
   **X Axis → Units: eV**
   **X Axis → Minimum value: -15**
   **X Axis → Maximum value: -2** then OK.
 [image]


Step 4: Run the calculation - BP86+U
====================================

Go back to the Main menu of amsinput, change to HubbardU menu, and
apply an U value of 0.6 a.u. to the d-orbitals of the Ni atom.

   Go to **Model → HubbardU**.
   Click the [image: AddButton][image]
   Set **Element** to **Ni**
   Set **UValue** to **0.6**
   Set **LValue** to **d**
 [image]

This will influence the Hamiltonian and results in a state which tries
to omit partial occupation or degeneracy with reference to the
d-orbitals.


Step 4a: Run the calculation
----------------------------

Now you can save and run the calculation.

   **File → Save As...**, give it a name and press Save.
   **File → Run**


Step 4b: Checking the results
-----------------------------

After the calculation finished, you can check the Output for the 'Band
Gap Info'.

   **SCM → Output**
   **Properties → Band Gap Info**

One can see that there is now a band gap of around 2 eV (still less
than the experimental value, but qualitatively more sensible).

[image]

Plotting and examining the partial density of states (pDOS) for this
calculation reveals that the d-orbital contributions of Ni are no
longer crossing the Fermi level.

   **SCM → DOS**
   Select the **Ni atom**.
   Choose **Partial → Ni(1) → d-DOS**
   You can move the legend with the mouse by drag and drop it to the desired location.
 [image]

You can also shift the Fermi energy to 0, if you prefer:

   **Graph → Shift Fermi Energy To Zero**
 [image]
