How can I calculate formation energy of a system (unit cell of bulk/supercell thin film) by using ab-initio DFT method (VASP in particular)?
As per of my understanding suppose I want to calculate formation energy for bulk Fe2VAl (gull Heusler alloy) then I should get it by using following Eform.=E(Fe2VAl) - 2*EFe -EV -EAl
If its right then my question is that what value should I take it of EFe , EV , and EAl ? Is it the energy value of Fe, V and Al calculated from a separate bulk calculation of Fe, V and Al for the respective crystal structure form in which they crystallizes individually or its some other value?
Please clarify my doubt, thanks in advance
sincerely
Rohit
https://www.researchgate.net/post/How_can_I_calculate_the_defect_formation_energy_by_DFT
http://pubs.acs.org/doi/pdf/10.1021/jp2051454
refer these links.......it will help you....
You have to calculate the energies of the individual elements in their respective ground states. Use the same psuedopotential for the energy calculations of the elements and of the compound.
Thanks a lot !
Choutipalli Venkata Surya Kumar and Ramachandran Sankarasubramanian for your responses.
The equation (Eform=E(Fe2VAl) - 2*EFe -EV -EAl) is correct for calculating formation energy. It just depends on the way we calculate EFe or EAl.
Iron is BCC and for the bulk calculation you will have to calculate the ground state energy of Fe in the BCC structure. If your POSCAR has 2 atoms then the energy value you will get upon relaxation is the energy of the structure which consists of 2 Fe atoms. Thus, to obtain EFe you will need to divide the structure energy by 2. Similarly, you can do the energy calculations for Al and V or any other element.
Hope this helps!
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