[Pw_forum] Calculation of lattic constants and bulk modulus od w-ZnO

[mohnish pandey]

Dear Muhammad,

Their is an easier way to calculate the optimized the lattice constant
which is based on calculation of stress and forces on the system. In the
flag "calculation" put "vc-relax" and in "ion_dynamics" put "bfgs" (there
are other options too) and in the  "cell_dynamics" put "bfgs" (again there
are other options also) and run the job. When the calculation is over the
code will print the final lattice vectors by which you can calculate the
optimized lattice constant. For further details look into
/quantum-espresso-folder/Doc/INPUT_PW.html


On Sun, May 13, 2012 at 2:52 AM, zafar rasheed <zafartariq2003 at yahoo.com>wrote:

> Dear All
>
> I want to calculate lattice constants a, and c and bulk modulus of w-ZnO.
> For this purpose:
>
>    1.
>
>    I take experimental lattice constants (a= 3.25 Ang. and c = 5.206 Ang.
>    and by changing these values into bohr.) and first take different values
>    above and below a and do scf calculations to optimize a. As in case of W
>    ZnO (Hexagonal and Trigonal P) ibrav= 4 and celldm(3) =c/a is used. So when
>    I change a (celldm (1))I have to change celldm (3). In this way I get
>    lattice constant a which is nearly same as experimental with 2 percent
>    error.
>    2.
>
>    Then I fix this lattice constant a (celldm (1)) and change lattice
>    constant c (By taking different values above and below experimental value
>    of c). As c changes celldm (3) also changes. In this way I get lattice
>    constant c which is very close to experimental lattice constant with a
>    little error of 2 percent.
>    3.
>
>    The output data for the calculation of c by fixing a I use to
>    calculate BULK modulus for ZnO. Again these results are comparable with
>    experimental and already calculated results by different techniques .
>    4.
>
>    Now I want to know that, Is my calculation procedure is right?
>
> Best Regards
>
> Muhammad Zafar
> PhD Scholar
> Department of Physics
> The Islamia University of Bahawalpur,Pakistan
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>


-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
BTech-Mtech, IIT Kanpur
Senior Project Associate,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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