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["Lu Fu-Fa" <g930102@ccit.edu.tw>]

Dear Christoph,

I am not sure it is what you want, but I have browsed the website:
 http://cst-www.nrl.navy.mil/lattice/spcgrp/hexagonal.html and
http://cst-www.nrl.navy.mil/lattice/struk/b8_2.html

I have test some input schemes, just one could be matched!

#Definition of the unit cell
acell   5.223/0.529177  5.223/0.529177   8.5666/0.529177            #
Lattice constant  a, b, c in Bohr unit
rprim   0.5   -0.8660254037844386  0.0    # HCP  reciprocal primitive
vectors
        0.5    0.8660254037844386  0.0    # (to be scaled by acell)
        0.0    0.0                 1.0

#Definition of the atom types
ntype 2           # There is only one type of atom
zatnum 30 12       # The keyword "zatnum" refers to the atomic number of the
                  # possible type(s) of atom. The pseudopotential(s)
                  # mentioned in the "files" file must correspond
                  # to the type(s) of atom. Here, the type 1 is the Zn.
                  # type 2 is the Mg.


#Definition of the atoms
natom 6           # There are six atoms
type 1 1 2 2 1  1      # type 1 : Zn, type 2 : Mg
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom

   0.000000000 0.000000000   0.00000     # Triplet giving the REDUCED
coordinate of atom 1.
   0.000000000 0.000000000   0.50000     # Triplet giving the REDUCED
coordinate of atom 2.
   0.333333333 0.666666667   0.25000     # Triplet giving the REDUCED
coordinate of atom 3.
   0.666666667 0.333333333   0.75000     # Triplet giving the REDUCED
coordinate of atom 4.
   0.666666667 0.333333333   0.25000     # Triplet giving the REDUCED
coordinate of atom 5.
   0.333333333 0.666666667   0.75000     # Triplet giving the REDUCED
coordinate of atom 6.

Output as follows:

 DATASET    1 : space group P6_3/m m c (#194); Bravais hP (primitive hexag.)
 DATASET    2 : space group P6_3/m m c (#194); Bravais hP (primitive hexag.)
...
May be or not for helping!

=======================================================
Lu Fu-Fa, Doctoral Student, E-mail: g930102@ccit.edu.tw
Semiconductors Lab., Dept. of Applied Physics
Chung Cheng Institute of Technology (CCIT), Taiwan
=======================================================

----- Original Message -----
From: <c.gross@physik.uni-frankfurt.de>
To: <forum@abinit.org>
Sent: Tuesday, July 22, 2003 11:36 PM
Subject: Re: Re: [abinit-forum] Definition of hexagonal cell / MgZn2


> Dear Masayoshi,
>
> Thanks for your reply. Maybe I misunderstood your reply, but I could not
fix my problem so far.
>
> First: You are right, multiplicity of the site (0,0,0) is 2. To be
complete, the Wyckoff positions of the three atoms in the asymmetric unit
are: Mg:4f, Zn1:2a, Zn2:6h. This sums up two 12 atoms per unit cell (4
formula units MgZn2 per unit cell, Z=4). The abinit Tutorial describes natom
as 'total number of atoms in unit cell', but if I try "natom 12 typat 1 2 2"
instead of the original "natom 3 typat 1 2 2", ABINIS stops with an error,
saying that it now expects 12 entries in the typat list. I am still unsure,
whether I have to specify all 12 (partially equivalent) positions in the
unit cell (I thought the 'Symmetry analyser' does this for me) or just the 3
positions in the asymmetric unit ? Could you be a bit more specific why the
original lines "natom 3 typat 1 2 2" look strange to you ?
>
> Second: Komura & Tokunaga have just chosen some other, but equivalent,
positions for their asymmetric unit (with some minor differences in the free
coordinates). However, if I retry with their data, I end up with the same
ABINIS warnings as in my first posting (see below).
>
> Thanks again,
> Christoph