[Pw_forum] minimization in CP molecular dynamics

[Brandon Wood]

Dear Mansoureh and Nicola,

If memory serves, the values printed at the end of the file represent 
averages throughout the course of the simulation rather than final 
values.  So ekinc <> 0 is actually expected, unless you start from an 
already converged electronic configuration (although your value is still 
surprisingly high).  It also means the total energy doesn't accurately 
represent your final configuration.

A better thing to do is to take a look at the data output for the 
_final_ CP timestep in your run.  If ekinc is still nonzero at that 
timestep, increase nstep.  In any case, it is much more efficient to use 
CG minimization.

Brandon

----------------------------------------------------------
Dr. Brandon C. Wood
NSF Postdoctoral Fellow, Theoretical Sciences Unit
Jawaharlal Nehru Centre for Advanced Scientific Research
Bangalore, India
----------------------------------------------------------

Nicola Marzari wrote:
> 
> Shouldn't ekinc be zero ? I forgot the name used, but in a properly
> executed CP calculation, in which you do damped dynamics on the
> electrons to reach the ground state at fixed ions, the kinetic energy
> of the electrons (as opposed to the quantum kinetic energy of your
> system, ekin) should be zero.
> 
> I suggest to anyone learning CP calculations (a very worthy
> endeavour, and one that would be extremely useful in the long
> run) to study carefully the review paper on the topic by Marx and
> Hutter,
> 
> http://www.theochem.ruhr-uni-bochum.de/research/marx/marx.pdf
> 
> CP in Q-E now can also do conjugate gradients minimization on
> the electrons (more efficient than damped dynamics) and, for
> metals, ensemble-dft (i.e. born-oppenheimer dynamics).
> 
> For cg/edft, there was one bug (memmory misallocation)
> for parallel execution, just found by by Brandon Wood. It'll
> be fixed in the cvs in the next few days.
> 
> 
> 			nicola
> 
> Mansoureh Pashangpour wrote:
>> Dear Paolo
>> I know one of them is in Ry and another one in Ha,but when I compare 
>> them they are different
>> scf:  total energy              =  -243.33284101 Ry
>>
>> CP:  ekinc         :       10.67409      10.67409 (AU)
>>    ekin          :      153.58930     153.58930 (AU)
>>    epot          :     -458.58466    -458.58466 (AU)
>>    totel energy  :     -258.18270    -258.18270 (AU)
>>    temperature   :        0.00000       0.00000 (K )
>>    enthalpy      :     -258.18270    -258.18270 (AU)
>>    econs         :     -258.18270    -258.18270 (AU)
>>    pressure      :       -3.47982      -3.47982 (Gpa)
>>    volume        :      488.11442     488.11442 (AU)
>> Thanks
>