QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Steven on September 10, 2017, 22:28

Title: Prediction of a strucure
Post by: Steven on September 10, 2017, 22:28

Sir
      I have experimental lattice parameters of a structure at 12 GPa (stable at this pressure)  . How can i model the structure at 0 GPa from the above information?

Title: Re: Prediction of a strucure
Post by: Daniele Stradi on September 11, 2017, 09:27

Hi,

this can be done by performing a geometry optimization of the structure, by allowing the unit cell to relax with a target pressure of 0 GPa.

Regards,
Daniele

Title: Re: Prediction of a strucure
Post by: Ulrik G. Vej-Hansen on September 11, 2017, 09:28

You can easily relax the lattice at no external pressure, but whether that is a good model for the material under those conditions is a scientific question, not a software question. In principle, you need to check if another structure is more stable at no external pressure, if you want to model the material under equilibrium conditions. You can use our crystal structure prediction tool for that: https://docs.quantumwise.com/tutorials/crystal_structure_prediction_tio2/crystal_structure_prediction_tio2.html

Title: Re: Prediction of a strucure
Post by: Steven on September 11, 2017, 13:06

Thank you sirs for the replies.
  If i do geometry optimization of the structure, should i preserve the symmetry (by constraining  bravais_lattice) or should i perform unconstrained?

Title: Re: Prediction of a strucure
Post by: Jess Wellendorff on September 11, 2017, 14:23

Depends on weather if wish to allow the geometry optimization to search for a minimum-energy crystal corresponding to a different Bravais lattice. In this case, I guess not, so I suggest you preserve the crystal symmetry.

Title: Re: Prediction of a strucure
Post by: Steven on September 11, 2017, 14:28

Thank you Sir ,
        I will be trying that