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[jmlv@imr.ac.cn]

Dear everyone,

I was trying step by step the examples in Tutorial #4: Aluminum, the bulk and 
the surface. But I got a problem in the middle of it. 

As we all know, the lattice constant of conventional unit cell for pure Al 
metal is a=7.6524 Bohr(4.0495 Angstrom). So the lattice constant for its 
primitive cell should be a*2^(-0.5)=5.4111 Bohr(2.8634 Angstrom).

However, in Tutorial 4.1-4.3, the primitive cell (1 atom in it) is obviously 
used, yet acell is set to 7.60 Bohr - the value for conventional unit cell. 
And surprisingly, the relaxed lattice constant is around 7.50 Bohr (for 
conventional unit cell), not around 5.4 Bohr (for primitive cell).

Is there anything wrong with the tutorial? Or I just misunderstood something? 
I was totally confused. Could anybody help me out here?

Thanks in advance.

Jianmin Lu, Ph.D.
Institute of Metal Research, Chinese Academy of Sciences.
72#, Wenhua Road, Shenyang, China.
E-mail:jmlv@imr.ac.cn