Inquire about the VASP Built-in Functionality for ZPE and Finite-Temperature Corrections.

[hszhao.cn@gmail.com]

Dear VASP Forum,

I am currently conducting research on crystal structural phase transitions induced by pressure and temperature using VASP calculations. For my studies on phase stability under different conditions, I need to know:

Does VASP have any built-in functionality to calculate zero-point energy (ZPE) and finite-temperature corrections for crystal structures? If so, could you briefly describe how to implement these features in my calculations?

I'm specifically interested in applying these corrections to improve the accuracy of my phase transition predictions in crystalline materials. I've seen in the literature (e.g., Shahi et al., Phys. Rev. B 97, 094111 (2018)) that for Si and Ge diamond-to-β-tin transitions, ZPE and finite-temperature (300K) phonon corrections can lower the transition pressure by approximately 1.3 GPa. Such corrections appear significant for accurate phase transition predictions.

Thank you for your assistance.

Best regards,
Zhao

[jonathan_lahnsteiner2]

Dear hszhao,

I would like to recommend you to read the following vasp wiki page where it is described how to compute the zero point energy and the finite temperature corrections. You will also find the corresponding links to the literature there.
For quasi-harmonic corrections you could try to use phonopy. A description of how to use phonopy for quasi harmonic corrections can be found here.

I hope these pages will help to clarify how to do a ZPE calculation.

All the best Jonathan

[hszhao.cn@gmail.com]

Dear Jonathan,

I would like to recommend you to read the following vasp wiki page where it is described how to compute the zero point energy and the finite temperature corrections. You will also find the corresponding links to the literature there.

Thank you for recommending the VASP wiki page on electron-phonon interactions from Monte-Carlo sampling. After reviewing it, I have several questions as the descriptions seem quite brief:

1. Regarding the generated POSCAR files (POSCAR.TEBEG.NUMBER for full MC sampling and POSCAR.TEMP for ZG configuration) - am I supposed to perform additional VASP calculations using each of these generated structures? What would be the complete workflow?

2. Can these methods directly output Gibbs free energy in the VASP results? If not, what additional steps would be needed to obtain the related thermodynamic properties to further obtain the Gibbs free energy?

3. The wiki page lacks detailed examples, and I couldn't find any relevant test cases, e.g., in the vasp.6.5.0/testsuite/tests directory. Could you point me to practical examples demonstrating the implementation and analysis of these methods?

I would appreciate any clarification or additional resources you might have on this topic.

Best regards,
Zhao

[jonathan_lahnsteiner2]

Dear hszhao,

Regarding your questions:
1) The one-shot method will generate POSCAR files for you for which you have to do VASP calculations with the desired settings and then extract the quantity of interest from the output files.
2)No with this method you will not be able to obtain the Gibbs free energy. There is no pressure dependence included in these calculations. This is why I tried to guide you to phonopy and the quasi harmonic approximation in my last post.
3)The vasp wiki contains a example page where a band gap renormalization is done using the tags you will need.

Please also read the research papers which are linked on the vasp wiki pages for the methods. These will give you more insight in the methods which you are using. The wiki is only a brief summary of these papers.

All the best Jonathan