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

[zafar rasheed]

Dear All
I want to calculate lattice constants
a, and c and bulk modulus of w-ZnO. For this purpose:
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. 
	
	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.
	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 .
	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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