Here, we will introduce how to calculate the work function of metal crystals.
Here, we will introduce how to calculate the work function of metal crystals.
Follow the procedure below.
1. Optimization of crystal structure
2. Slab model creation
3. ESM model creation
4. Structural optimization to which the ESM method is applied
5. Work function value comparison
First of all, the calculation is performed with Li of the BCC structure obtained from Material Projects. I used Quantum ESPRESSO as the calculation software.
Table 1 Lattice constants of Materials Projects and Quantum ESPRESSO
Create a metal slab model based on the optimized crystal structure. It is also possible to create using the slab model installed in Exabyte.io or NanoLabo.
Here, 100 faces, 110 faces, and 111 faces were created.
* NanoLabo can also be used on Exabyte.io.
By using the ESM method function of Quantum ESPRESSO, it is possible to obtain accurately without taking a lot of vacuum layers. Therefore, here, we will create a model for calculation using the ESM method function of Quantum ESPRESSO. The model is created from "Boundary Conditions". This time, I chose bc3 as the Type.
Save the ESM model you created.
Exabyte.io provides a computational workflow that uses the ESM method. This time, we will use “Effective Screening Medium (ESM) Relax”.
The calculation result is displayed as below.
By using the ESM method, the potential at the end becomes a value of zero, so the value with the sign of the Fermi level changed becomes the work.
The result of comparing the value of the work function and the experimental value in each azimuth plane is shown.
Table 2 Work function values and experimental values for each orientation plane
The calculation result shows a value close to the experimental value. The average value for all faces is 2.95 eV, which is even closer to the experimental value.
[1] APOvchinnikov and BMTsarev, Sov.Phys.-Solid State 9 (1968) 2766
Original Source from: https://ctc-mi-solution.com/esm法を利用した仕事関数の計算方法/
