[Wien] excited state of a system

[Stefaan Cottenier]

 > But is your reply indicating that.......
> 
> the excited states *may be* those states having higher energy....but it 
> is *not sure* that whether the states having higher energy will be the 
> excited states of the system??......Please assure me that this is the 
> meaning of your reply...........

Yes.

> but if this is the meaning then another 
> question is that may it be happened that some converged solutions of the 
> system actually never be found in reality??...

Sure. You examined only ferromagnetic, antiferromagnetic and 
'non-magnetic' states. But for sure there are many more magnetic 
configurations for which you can get a converged solution. And the same 
holds also for the structural degrees of freedom: you will find 
converged solutions for your solid in e.g. bcc, fcc, ... crystal 
structures. No way to find all these many situations if you increase the 
temperature.

> if this is true then the question is why?

Many possible reasons:

* all calculated information is at 0 K. Phonons and all kinds of 
electronic excitations will enter the game at temperatures above 0 K, 
and these might alter the picture.
* something else might have happened before (e.g. a structural phase 
transition occurs before you reach the point where a magnetic phase 
transition in the original material would have occurred)
* some solutions correspond to saddlepoints, and will spontaneously 
evolve to another solution
* your material might be molten before you reach the energy 
corresponding to a particular case
*...

Stefaan