Yes, I must say it can be done

Use Fallout software to work

thank you very much

Dear David Kwaku Danso

In addition to Prof. Soheil Seyed Hosseini suggestion, you can check the following software:

https://www.fplo.de/

That was the only one code I wanted to learn, but I couldn´t afford it. However it has some wonderful applications to solid state physics such as:

Article Lifshitz transitions in RCo5 (R=Y, La) and in Osmium

computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals, i.e. functions of another function, which in this case is the spatially dependent electron density. Hence the name density functional theory comes from the use of functionals of the electron density. DFT is among the most popular and versatile methods available in condensed-matter physics, computational physics, and computational chemistry.

DFT has been very popular for calculations in solid-state physics since the 1970s. However, DFT was not considered accurate enough for calculations in quantum chemistry until the 1990s, when the approximations used in the theory were greatly refined to better model the exchange and correlation interactions. Computational costs are relatively low when compared to traditional methods, such as exchange only Hartree–Fock theory and its descendants that include electron correlation. Since, DFT has become an important tool for methods of nuclear spectroscopy such as Mössbauer spectroscopy or perturbed angular correlation, in order to understand the reason of specific electric field gradients in crystals.

Despite recent improvements, there are still difficulties in using density functional theory to properly describe: intermolecular interactions (of critical importance to understanding chemical reactions), especially van der Waals forces (dispersion); charge transfer excitations; transition states, global potential energy surfaces, dopant interactions and some strongly correlated systems; and in calculations of the band gap and ferromagnetism in semiconductors.[1] The incomplete treatment of dispersion can adversely affect the accuracy of DFT (at least when used alone and uncorrected) in the treatment of systems which are dominated by dispersion (e.g. interacting noble gas atoms)[2] or where dispersion competes significantly with other effects (e.g. in biomolecules).[3] The development of new DFT methods designed to overcome this problem, by alterations to the functional[4] or by the inclusion of additive terms,[5][6][7][8] is a current research topic.

computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals, i.e. functions of another function, which in this case is the spatially dependent electron density. Hence the name density functional theory comes from the use of functionals of the electron density. DFT is among the most popular and versatile methods available in condensed-matter physics, computational physics, and computational chemistry.

DFT has been very popular for calculations in solid-state physics since the 1970s. However, DFT was not considered accurate enough for calculations in quantum chemistry until the 1990s, when the approximations used in the theory were greatly refined to better model the exchange and correlation interactions. Computational costs are relatively low when compared to traditional methods, such as exchange only Hartree–Fock theory and its descendants that include electron correlation. Since, DFT has become an important tool for methods of nuclear spectroscopy such as Mössbauer spectroscopy or perturbed angular correlation, in order to understand the reason of specific electric field gradients in crystals.

Despite recent improvements, there are still difficulties in using density functional theory to properly describe: intermolecular interactions (of critical importance to understanding chemical reactions), especially van der Waals forces (dispersion); charge transfer excitations; transition states, global potential energy surfaces, dopant interactions and some strongly correlated systems; and in calculations of the band gap and ferromagnetism in semiconductors.[1] The incomplete treatment of dispersion can adversely affect the accuracy of DFT (at least when used alone and uncorrected) in the treatment of systems which are dominated by dispersion (e.g. interacting noble gas atoms)[2] or where dispersion competes significantly with other effects (e.g. in biomolecules).[3] The development of new DFT methods designed to overcome this problem, by alterations to the functional[4] or by the inclusion of additive terms,[5][6][7][8] is a current research topic.

computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals, i.e. functions of another function, which in this case is the spatially dependent electron density. Hence the name density functional theory comes from the use of functionals of the electron density. DFT is among the most popular and versatile methods available in condensed-matter physics, computational physics, and computational chemistry.

DFT has been very popular for calculations in solid-state physics since the 1970s. However, DFT was not considered accurate enough for calculations in quantum chemistry until the 1990s, when the approximations used in the theory were greatly refined to better model the exchange and correlation interactions. Computational costs are relatively low when compared to traditional methods, such as exchange only Hartree–Fock theory and its descendants that include electron correlation. Since, DFT has become an important tool for methods of nuclear spectroscopy such as Mössbauer spectroscopy or perturbed angular correlation, in order to understand the reason of specific electric field gradients in crystals.

Despite recent improvements, there are still difficulties in using density functional theory to properly describe: intermolecular interactions (of critical importance to understanding chemical reactions), especially van der Waals forces (dispersion); charge transfer excitations; transition states, global potential energy surfaces, dopant interactions and some strongly correlated systems; and in calculations of the band gap and ferromagnetism in semiconductors.[1] The incomplete treatment of dispersion can adversely affect the accuracy of DFT (at least when used alone and uncorrected) in the treatment of systems which are dominated by dispersion (e.g. interacting noble gas atoms)[2] or where dispersion competes significantly with other effects (e.g. in biomolecules).[3] The development of new DFT methods designed to overcome this problem, by alterations to the functional[4] or by the inclusion of additive terms,[5][6][7][8] is a current research topic.

Dear David Kwaku Danso ,

I have done many CASTEP simulations of Al2O3, in fact it's one of the standard benchmark systems for CASTEP, so it is certainly possible to simulate it well. In order to understand what's going wrong for your study, please could you let us know:

- which input structure you used (corundum? Primitive unit cell or something larger?)

- which exchange-correlation functional

- what k-point sampling you used

- which pseudopotentials you used and what plane-wave cut-off energy

You could attach your input CELL and PARAM file too, which would enable us to see any other settings which might be relevant.

All the best,

Phil Hasnip

(CASTEP Developer)

Thank you, Philip. I am done now with the simulation.

Dear Philip,

Recently, i have simulate a material in castep code. The problem that i face, the input is a body centred tetragonal symmetry but after optimization it becomes trigonal structure. I have done this calculation in different way and used both GGA and LDA. but got the same result. Could you please tell me what is the region for this structural change?

Dear M N H Liton ,

This is very hard to answer without knowing more about your material. Perhaps you could email the academic CASTEP support email list and attach some input files, and I can respond there. That way, anyone else with that issue will also benefit. If it's a general problem I can post a follow-up on this thread.

Phil

Thank you @ Dear Philip James Hasnip

Philip James Hasnip , Please with regards to the calculation of elastic constants from total energy, I see that CASTEP uses the stress-strain method instead of energy-strain method. Can you please give me the reference journal paper for the type of stress-strain method used in the CASTEP code. A lot of papers which have used CASTEP from materials studio give different references concerning the method used.

David Kwaku Danso I'm not quite sure what you mean, do you mean the reference for the elastic constants Python script, or how to calculate the stress in DFT, or something else? You can of course do energy-strain with CASTEP if you prefer, it's just less efficient.

Whichever method you use, you must make sure to use the finite basis-set correction, otherwise it will be difficult to get accurate results:

Article Finite Gasis Eet Corrections to Total Energy Pseudopotential...

This is implemented in CASTEP automatically when you request a stress calculation, but it you don't request the stress then you should activate it yourself by adding the following line to your .param file:

finite_basis_corr : automatic

Hope that helps,

Phil

Dear Philip James Hasnip,

if you can help me to calculate the elastic properties in function of pressure by the castep code implemented in the software biovia materiel studio