[Pw_forum] About trust_radius

[stefano de gironcoli]

well... bfgs does not do random moves but choose the search direction on 
the basis of the forces and of the current estimate for the inverse 
hessian matrix... as the system is typically not in a quadratic regime 
(at least at the beginning) it does not trust the resulting step to its 
full size but limits the move to a given trust_radium that is update 
during the evolution starting from an initial value and limited to be 
between a minimum and a maximum...
all these parametera can be set in input using the variables you are 
referring to ...

stefano

On 11/11/2014 05:19 PM, robert.guzman wrote:
> Hi everyone.
>
> What is the meaning of trust_radius_ini, trust_radius_max,
> trust_radius_min?
>
> I am supposing that:
> if trust_radius_ini = 1.d-2 then QE moves all the atoms of the unit cell
> in 0.00529 A in a random way. And after the QE calculates the forces and
> the new displacements? and if the displacement of one atom (d_a) is
> greater than "trust_radius_max" then QE makes that
> "d_a=trust_radius_max" in the direction of the force.
>
> I didn't found this information in the web. Please someone can help me?
>
> Best Regards.
>
> Mgter. R. M. Guzmán A.
> Insituto Balseiro. Argentina.
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