AkijiYamamotoYAMAMOTO.Akiji@nims.go.jp
National Institute for Materials Science, Tsukuba, Ibaraki, 305, Japan
Wyckoff positions of Space groups for Dihedral quasicrystals I : Decagonal groups |
Wyckoff positions of decagonal space groups are given.
Abstract:
Wyckoff positions of five-dimensional decagonal, octagonal and
dodecagonal space groups are calculated to facilitate the model
building and structure analysis of dihedral quasicrystals. The
Wyckoff positions in the decagonal ones and their representative
coordinates are given. The Wyckoff positions of octagonal and
dodecagonal ones together with the orbits of Wyckoff positions are
available in the web site (http://wcp2-ap.eng.hokudai.ac.jp/yamamoto/)
1 Introduction
The program Carat implemented in the program package GAP is applied to
the dihedral space groups. This requires only the matrix
representation of the point group and calculate the normalizer for
classifying the generated space groups. All the possible space groups
in these quasicrystals are known and tabulated.[4]
However, the known tables are calculated under different equivalence
relations, where the scaling transformations of the dihedral lattice
is not taken into account and enantiomorphic pairs are regarded as
independent. We employ the affine equivalence as in Carat. Then
the classification in this paper is broader than that in the present
paper, leading to a smaller number of non-equivalent space groups.
In the structure analysis of quasicrystals, the tables of Wyckoff
positions are useful, since the number of independent parameters of an
occupation domain (OD) is determined by the site symmetry of the
center of the OD. The shape of ODs is also restricted by the site
symmetry. The symmetry of the OD should be higher than or equal to the
site symmetry. Thus the Wyckoff positions and their site symmetry are
fundamental information of quasicrystallography. The method of
calculating Wyckoff position is established but there are no tables of
all Wyckoff positions of quasicrystals. This paper calculates those of
decagonal, octagonal and dodecagonal quasicrystals, since they are
found so far. In this paper, tables only for the decagonal
quasicrystals are given but other more comprehensive tables are
accessible in the web.(http://wcp-ap.eng.hokudai.ac.jp/yamamoto/)
2 Calculation Method
We use Carat in GAP package as in a previous
paper.[2, 9] The n× n matrix
representations of a point group is necessitated in Carat. The point
group of axial quasicrystals is a dihedral group or its
subgroup. Therefore it is given by one p-fold rotation or
rote-inversion (p>2) and one 2-fold rotation or mirror. For
centrosymmetric groups, we use one p-fold rotation (p>2) and one
2-fold axis and inversion. All the cases, there is only a primitive
lattice, although pentagonal space groups have the primitive and one
centered lattice, which is called Q-centered
lattice.[3, 4]
| Table 1: The generators of the decagonal space groups (excluding those
for lattice translations) employed in Tables 2-7. [R10≡
−u,x+y+z+u,−x,−y,v, R21≡ −u,−z,−y,−x,−v, R22≡
u,z,y,x,−v, σz≡ x,y,z,u,−v, I≡
−x,−y,−z,−u,−v, τ0=(0,0,0,0,0),τ1=(0,0,0,0,1)/2,
τ2=(0,0,0,0,1)/10, τ3=(0,0,0,0,1)/5] Note that
P10122(10722) is equivalent to P10322(10722) and
P10222(10722) to P10422(10722) since
they are related by the scaling transformation of the decagonal
lattice. |
| Space group | generators |
| P10/mmm(1071mm) | {R10|τ0},{R21|τ0},{I|τ0} |
| P10/mcc(1071mm) | {R10|τ0},{R21|τ1},{I|τ0} |
| P105/mcm(1071mm) | {R10|τ1},{R21|τ0},{I|τ0} |
| P105/mmc(1071mm) | {R10|τ1},{R21|τ1},{I|τ0} |
| P10mm(107mm) | {R10|τ0},{R21|τ0} |
| P10cc(107mm) | {R10|τ0},{R21|τ1} |
| P105cm(107mm) | {R10|τ1},{R21|τ0} |
| P105mc(107mm) | {R10|τ1},{R21|τ1} |
| P10 22(107mm) | {R10|τ0},{R21|τ0} |
| P10122(107mm) | {R10|τ2},{R21|τ0} |
| P10222(107mm) | {R10|τ3},{R21|τ0} |
| P10522(107mm) | {R10|τ1},{R21|τ0} |
| P10/m(1071) | {R10|τ0},{σz|τ0} |
| P105/m(1071) | {R10|τ1},{σz|τ0} |
| P10(107) | {R10|τ0} |
| P101(107) | {R10|τ2} |
| P102(107) | {R10|τ3} |
| P105(107) | {R10|τ1} |
| P102m(5mm) | {IR10|τ0},{R21|τ0} |
| P102c(5mm) | {IR10|τ0},{R21|τ1} |
| P10m2(5mm) | {IR10|τ0},{R22|τ0} |
| P10c2(5mm) | {IR10|τ0},{R22|τ1} |
| P10(5) | {IR10|τ0} |
3 Discussion
The decagonal quasicrystals have several different space groups. The
space groups used in the structure analysis so fat are
P105/mmc(1071mm), P105mc(107mm), 10(5),
P10m2(5mm) and P102c(5mm)
[8, 7, 1, 5, 6]
However, the decagonal quasicrystals analized so far are limitted to
the cases with the period ≃ 4, 8, 12 Å along the 10-fold
axis. Some decagonal quasicrystals have 16Å period. In d-Al-Ni-Co,
there are at least 5 quasicrystal phases. Among them, three phases are
determined. The unsolved structures may necessitate other space groups.
| Table 2: The Wyckoff positions of the space groups
P10/mmm(1071mm). The first column represents Wyckoff symbol
(W.S.). The second and third columns denote the site symmetry and
the representative coordinates, respectively. |
| W.S. | site symmetry | coordinates |
| 1a | 10/mmm(1071mm) | (0,0,0,0,0) |
| 1b | 10/mmm(1071mm) | (0,0,0,0,1/2) |
| 2a | 10m(5m) | (1/5,1/5,1/5,1/5,0) |
| 2b | 10m(5m) | (1/5,1/5,1/5,1/5,1/2) |
| 2c | 10m(5m) | (2/5,2/5,2/5,2/5,0) |
| 2d | 10m(5m) | (2/5,2/5,2/5,2/5,1/2) |
| 5a | mmm(mm1) | (1/2,0,0,1/2,0) |
| 5b | mmm(mm1) | (1/2,0,0,1/2,1/2) |
| 5c | mmm(mm1) | (0,1/2,1/2,0,0) |
| 5d | mmm(mm1) | (0,1/2,1/2,0,1/2) |
| 5e | mmm(mm1) | (1/2,1/2,1/2,1/2,0) |
| 5e | mmm(mm1) | (1/2,1/2,1/2,1/2,1/2) |
| 2e | 10mm(107mm) | (0,0,0,0,v) |
| 4e | 5m(52m) | (1/5,1/5,1/5,1/5,v) |
| 4f | 5m(52m) | (2/5,2/5,2/5,2/5,v) |
| 10a | mm2(mm1) | (1/2,0,0,1/2,v) |
| 10b | mm2(mm1) | (0,1/2,1/2,0,v) |
| 10c | mm2(mm1) | (1/2,1/2,1/2,1/2,v) |
| 10d | 2mm(mm) | (x,y,−y,−x,0) |
| 10e | 2mm(mm) | (x,y,−y,−x,1/2) |
| 10f | mm2(m) | (x,y,−y,−x,v) |
| 10g | mm2(m) | (x,y,y,x,v) |
| 20a | m(1) | (x,y,z,u,0) |
| 20b | m(1) | (x,y,z,u,1/2) |
| 40a | 1(1) | (x,y,z,u,v) |
| Table 3: The Wyckoff positions of the space groups
P10/mcc(1071mm). |
| W.S. | site symmetry | coordinates |
| 2a | 10/m(1071) | (0,0,0,0,0) |
| 2b | 1022(107mm) | (0,0,0,0,1/4) |
| 2c | 1022(5mm) | (1/5,1/5,1/5,1/5,0) |
| 2d | 1022(5mm) | (2/5,2/5,2/5,2/5,0) |
| 2e | 52(10m) | (1/5,1/5,1/5,1/5,1/4) |
| 2f | 52(10m) | (2/5,2/5,2/5,2/5,1/4) |
| 10a | m2m(mm1) | (0,0,0,1/2,0) |
| 10b | m2m(mm1) | (0,0,1/2,0,0) |
| 10c | m2m(mm1) | (0,1/2,1/2,1/2,0) |
| 10d | 222(mm1) | (1/2,0,0,1/2,1/4) |
| 10d | 222(mm1) | (0,1/2,1/2,0,1/4) |
| 10e | 222(mm1) | (1/2,1/2,1/2,1/2,1/4) |
| 4a | 10(107) | (0,0,0,0,v) |
| 4b | 10(107) | (1/5,1/5,1/5,1/5,v) |
| 4c | 10(107) | (2/5,2/5,2/5,2/5,v) |
| 10a | mm2(mm1) | (0,0,0,1/2,v) |
| 10b | mm2(mm1) | (0,0,1/2,0,v) |
| 10b | mm2(mm1) | (0,1/2,1/2,1/2,v) |
| 10d | 2/m(mm) | (x,y,−y,−x,1/4) |
| 10f | m(m) | (x,y,y,x,1/4) |
| 20a | m(1) | (x,y,z,u,0) |
| 40a | 1(1) | (x,y,z,u,v) |
| Table 4: The Wyckoff positions of the space groups
P105/mmc(1071mm). |
| W.S. | site symmetry | coordinates |
| 2a | 10m(5m) | (0,0,0,0,3/4) |
| 2c | 10m(5m) | (1/5,1/5,1/5,1/5,3/4) |
| 2d | 10m(5m) | (1/5,1/5,1/5,1/5,1/4) |
| 2e | 10m(5m) | (2/5,2/5,2/5,2/5,3/4) |
| 2f | 10m(5m) | (2/5,2/5,2/5,2/5,1/4) |
| 2b | 5m(109m) | (0,0,0,0,0) |
| 10a | 2/m(mm) | (1/2,0,0,1/2,0) |
| 10b | 2/m(mm) | (0,1/2,1/2,0,0) |
| 10c | 2/m(mm) | (1/2,1/2,1/2,1/2,0) |
| 4a | 5m(52m) | (0,0,0,0,v) |
| 4b | 5m(52m) | (1/5,1/5,1/5,1/5,v) |
| 4c | 5m(52m) | (2/5,2/5,2/5,2/5,v) |
| 10f | 2/m(mm) | (x,y,y,x,3/4) |
| 20f | 2(m) | (x,y,−y,−x,0) |
| 20f | m(m) | (x,y,y,x,v) |
| 20a | m(1) | (x,y,z,u,0) |
| 40a | 1(1) | (x,y,z,u,v) |
| Table 5: The Wyckoff positions of the space groups
P105/mcm(1071mm). |
| W.S. | site symmetry | coordinates |
| 2a | 10mm(5mm) | (0,0,0,0,3/4) |
| 2b | 5m(5m) | (0,0,0,0,0) |
| 2c | 10(5) | (1/5,1/5,1/5,1/5,3/4) |
| 2d | 10(5) | (2/5,2/5,2/5,2/5,3/4) |
| 2e | 52(52m) | (1/5,1/5,1/5,1/5,0) |
| 2f | 52(52m) | (2/5,2/5,2/5,2/5,0) |
| 10a | 2/m(m1) | (1/2,0,0,1/2,0) |
| 10b | 2/m(m1) | (0,1/2,1/2,0,0) |
| 10c | 2/m(m1) | (1/2,1/2,1/2,1/2,0) |
| 4a | 5m(52m) | (0,0,0,0,v) |
| 8a | 5(52) | (1/5,1/5,1/5,1/5,v) |
| 8b | 5(52) | (2/5,2/5,2/5,2/5,v) |
| 10d | 2/m(mm) | (x,y,−y,−x,3/4) |
| 20a | 2(m) | (x,y,y,x,0) |
| 20b | m(m) | (x,y,−y,−x,v) |
| 20c | m(m) | (x,y,z,u,3/4) |
| 40a | 1(1) | (x,y,z,u,v) |
The solved structures are analyzed and described without using tables
of Wyckoff positions, since no tables were present. The refined
parameter tables are given in the papers but neither Wyckoff symbols
nor site symmetry symbols have not been given. Although we can
calculate the site symmetry if the coordinates of the OD center are
known and in the refinement promgam for quasicrystals, Qcdiff, written
by the author, the site symmetry is calculated from the
coordinates. However, it may not be easy to know the site
symmetry from the coordinates, since it depends on the space group.
Therefore the table of refined structural parameters together with the
Wyckoff symbols is useful to know symmetrical information of
quasicrystal structures, as is so in conventional crystals. The tables
listed in this paper will be useful for the description of the
quasicrystal structures.
| Table 6: The Wyckoff positions of the space groups
P10mm(107mm). |
| P10mm(107mm) |
| W.S. | site symmetry | coordinates |
| 1a | 10mm(107mm) | (0,0,0,0,v) |
| 1b | 10mm(107mm) | (1/5,1/5,1/5,1/5,v) |
| 1c | 10mm(1071mm) | (2/5,2/5,2/5,2/5,v) |
| 5a | mm2(mm1) | (1/2,0,0,1/2,v) |
| 5b | mm2(mm1) | (1/2,0,0,1/2,v) |
| 5c | mm2(mm1) | (0,1/2,1/2,0,v) |
| 5e | mm2(mm1) | (1/2,1/2,1/2,1/2,v) |
| 10a | m(m) | (x,y,−y,−x,v) |
| 10b | m(m) | (x,x,0,y,z) |
| 20a | 1(1) | (x,y,z,u,v) |
| Table 7: The Wyckoff positions of the space group P1022(107mm). |
| P1022(107mm) |
| W.S. | site symmetry | coordinates |
| 1a | 1022(107mm) | (0,0,0,0,0) |
| 1a | 1022(107mm) | (0,0,0,0,1/2) |
| 1b | 1022(107mm) | (1/5,1/5,1/5,1/5,0) |
| 1c | 1022(107mm) | (1/5,1/5,1/5,1/5,1/2) |
| 1c | 1022(1071mm) | (2/5,2/5,2/5,2/5,0) |
| 1d | 1022(1071mm) | (2/5,2/5,2/5,2/5,1/2) |
| 5a | 222(mm1) | (1/2,0,0,1/2,0) |
| 5a | 222(mm1) | (1/2,0,0,1/2,1/2) |
| 5b | 222(mm1) | (1/2,0,0,1/2,v) |
| 5c | 222(mm1) | (0,1/2,1/2,0,0) |
| 5c | 222(mm1) | (0,1/2,1/2,0,1/2) |
| 5e | 222(mm1) | (1/2,1/2,1/2,1/2,0) |
| 5e | 222(mm1) | (1/2,1/2,1/2,1/2,1/2) |
| 2a | 10(107) | (0,0,0,0,v) |
| 2e | 10(107) | (1/5,1/5,1/5,1/5,v) |
| 2e | 10(107) | (2/5,2/5,2/5,2/5,v) |
| 10a | 2(1) | (0,0,0,1/2,v) |
| 10b | 2(1) | (0,0,1/2,1/2,v) |
| 10c | 2(1) | (0,1/2,0,1/2,v) |
| 10d | 2(m) | (x,y,−y,−x,0) |
| 10e | 2(m) | (x,y,−y,−x,1/2) |
| 10f | 2(m) | (x,x+2y,2x+2y,x+y,0) |
| 10g | 2(m) | (x,x+2y,2x+2y,x+y,1/2) |
| 20a | 1(1) | (x,y,z,u,v) |
| Table 8: The Wyckoff positions of the space groups
P102m(5mm). |
| P102m(5mm) |
| W.S. | site symmetry | coordinates |
| 1a | 102m(5mm) | (0,0,0,0,0) |
| 1b | 102m(5mm) | (0,0,0,0,1/2) |
| 1c | 102m(5mm) | (1/5,1/5,1/5,1/5,0) |
| 1d | 102m(5mm) | (1/5,1/5,1/5,1/5,1/2) |
| 1e | 102m(5mm) | (2/5,2/5,2/5,2/5,0) |
| 1f | 102m(5mm) | (2/5,2/5,2/5,2/5,1/2) |
| 1g | 102m(5mm) | (3/5,3/5,3/5,3/5,0) |
| 1h | 102m(5mm) | (3/5,3/5,3/5,3/5,1/2) |
| 1i | 102m(5mm) | (4/5,4/5,4/5,4/5,0) |
| 1j | 102m(5mm) | (4/5,4/5,4/5,4/5,1/2) |
| 5a | mm2(mm1) | (0,0,0,0,v) |
| 5a | mm2(mm1) | (1/5,1/5,1/5,1/5,v) |
| 5a | mm2(mm1) | (2/5,2/5,2/5,2/5,v) |
| 5a | mm2(mm1) | (3/5,3/5,3/5,3/5,v) |
| 5a | mm2(mm1) | (4/5,4/5,4/5,4/5,v) |
| 5a | mm2(mm1) | (1/2,0,0,1/2,1/2) |
| 5b | mm2(mm1) | (1/2,0,0,1/2,v) |
| 5c | mm2(mm1) | (0,1/2,1/2,0,0) |
| 5c | mm2(mm1) | (0,1/2,1/2,0,1/2) |
| 5e | mm2(mm1) | (1/2,1/2,1/2,1/2,0) |
| 5e | mm2(mm1) | (1/2,1/2,1/2,1/2,1/2) |
| 10a | 2(m) | (x,y,−y,−x,0) |
| 10b | 2(m) | (x,y,−y,−x,1/2) |
| 10c | 2(m) | (x,y,z,u,0) |
| 10d | 2(m) | (x,y,z,u,1/2) |
| 20a | 1(1) | (x,y,z,u,v) |
| Table 9: The Wyckoff positions of the space group
P10m2(5mm). |
| P10m2(5mm) |
| W.S. | site symmetry | coordinates |
| 1a | 10m2(m5mm) | (0,0,0,0,0) |
| 1a | 10m2(5mm) | (0,0,0,0,1/2) |
| 1b | 10m2(5mm) | (1/5,1/5,1/5,1/5,0) |
| 1b | 10m2(5mm) | (1/5,1/5,1/5,1/5,1/2) |
| 1c | 10m2(5mm) | (2/5,2/5,2/5,2/5,0) |
| 1c | 10m2(5mm) | (2/5,2/5,2/5,2/5,1/2) |
| 5a | mm2(mm1) | (0,0,0,0,v) |
| 5a | mm2(mm1) | (1/5,1/5,1/5,1/5,v) |
| 5a | mm2(mm1) | (2/5,2/5,2/5,2/5,v) |
| 10a | 2/m(m1) | (x,y,−y,−x,0) |
| 10b | 2/m(m1) | (x,y,−y,−x,1/2) |
| 10a | 2(m) | (x,y,−y,−x,z) |
| 10c | m(1) | (x,y,z,u,0) |
| 10d | m(1) | (x,y,z,u,1/2) |
| 20a | 1(1) | (x,y,z,u,v) |
| Table 10: The Wyckoff positions of the space groups
P10(5). |
| P10(5) |
| W.S. | site symmetry | coordinates |
| 1a | 10(5) | (0,0,0,0,0) |
| 1a | 10(5) | (0,0,0,0,1/2) |
| 1b | 10(5) | (1/5,1/5,1/5,1/5,0) |
| 1b | 10(5) | (1/5,1/5,1/5,1/5,1/2) |
| 1c | 10(5) | (2/5,2/5,2/5,2/5,0) |
| 1c | 10(5) | (2/5,2/5,2/5,2/5,1/2) |
| 1c | 10(5) | (3/5,3/5,3/5,3/5,0) |
| 1c | 10(5) | (3/5,3/5,3/5,3/5,1/2) |
| 1c | 10(5) | (4/5,4/5,4/5,4/5,0) |
| 1c | 10(5) | (4/5,4/5,4/5,4/5,1/2) |
| 1a | 5(52) | (0,0,0,0,v) |
| 1b | 5(52) | (1/5,1/5,1/5,1/5,v) |
| 1c | 5(52) | (2/5,2/5,2/5,2/5,v) |
| 1c | 5(52) | (3/5,3/5,3/5,3/5,v) |
| 1c | 5(52) | (4/5,4/5,4/5,4/5,v) |
| 10c | m(1) | (x,y,z,u,0) |
| 10d | m(1) | (x,y,z,u,1/2) |
| 20a | 1(1) | (x,y,z,u,v) |
| Table 11: The Wyckoff positions of the space groups
P10(107). |
| P10(107) |
| W.S. | site symmetry | coordinates |
| 1a | 5(52) | (0,0,0,0,v) |
| 1b | 5(52) | (1/5,1/5,1/5,1/5,v) |
| 1c | 5(52) | (2/5,2/5,2/5,2/5,v) |
| 1c | 5(52) | (3/5,3/5,3/5,3/5,v) |
| 1c | 5(52) | (4/5,4/5,4/5,4/5,v) |
| 10c | m(1) | (x,y,z,u,0) |
| 10d | m(1) | (x,y,z,u,1/2) |
| 20a | 1(1) | (x,y,z,u,v) |
4 Summary
The Wyckoff positions of decagonal, octagonal and dodecagonal space
groups for quasicrystals were calculated by the program Carat
implemented in the package GAP and listed for the decagonal space
groups. The Wyckof symbols and their site symmetries are given. Tables
for the octagonal and dodecagonal space groups and all equivalent
positions for each Wyckoff positions are obtainable from the web.
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