A I Tursina, A V Gribanov, N G Buknan'ko - Chemistry of metals and alloys - страница 1

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Chemistry of Metals and Alloys

Chem. Met. Alloys 1 (2008) 62-66 Ivan Franko National University of Lviv www.chemetal-j ournal. org

Crystal structure of the novel compound Ce3Pt4Al6

A.I. TURSINA1 *, A.V. GRIBANOV1, N.G. BUKHAN'KO1, P. ROGL2, Y.D. SEROPEGIN1

1 Department of Chemistry, Moscow State University, Leninskie Gory, 119992 GSP-2 Moscow, Russia

2 Institutfur Physikalische Chemie der Universitat Wien, Wahringerstrafie 42, A-1090 Wien, Austria * Corresponding author. Fax: +7 495 9390171; e-mail: tursina@newmail.ru

Received January 24, 2008; accepted February 17, 2008; available on-line March 31, 2008

The structure of the novel ternary aluminide Ce3Pt4Al6 was refined from X-ray single crystal data in the orthorhombic space group Pnma with a = 13.6589(2), b = 4.3331(1), c = 17.4740(3) A, Z = 4; R = 0.049. The structure can be described as built up from platinum centered trigonal prisms formed by cerium and aluminum atoms. These prisms form infinite columns in the [010] direction by sharing triangular faces. The columns are condensed into groups by edge sharing of the constituent trigonal prisms.

Cerium platinum aluminide / X-ray crystal structure determination / Ce3Pt4Al6

1. Introduction

In previous papers we have reported on the crystal structures of the new compounds CePt3Al5, which belongs to the site exchange YNi5Si3 structure type [1], Ce0.67Pt2Als with Gd0.67Pt2Als type- and Ce133Pt3Al8 with Gd133Pt3Al8-type structure [2]. Further studies of the Ce-Pt-Al ternary system revealed the existence of one more new compound, Ce3Pt4Al6.

Up to now, only two structures with the general formula RE3T4M6 (RE - rare earth, T - transition element, M - p-element) are known from the literature: Ce3Pt4Ge6 [3], crystallizing in the space group Cmcm, a = 4.419(1), b = 26.222(5), c = 4.422(1) A and its monoclinically deformed variant Y3Pt4Ge6 [4], crystallizing in the space group P21/m, a = 8.692(3), b = 4.3062(8), c = 13.162(3) A, в = 99.45(4)°

2. Experimental details

A sample with the nominal composition Ce33Pt22Al45 was arc-melted under high-purity argon from the elements (Ce 99.85, Pt 99.99, Al 99.99 wt.%). Mass loss was less than 1 wt.%. The sample was annealed in an evacuated quartz tube at 550°C for one month, then quenched in cold water. A single crystal with the dimensions 0.05mm><0.05mm><0.045 mm was extracted from the surface of the alloy.

X-ray diffraction was carried out with a Nonius Kappa CCD diffractometer using graphite-monochromatized MoKa radiation. Most of the atoms were located by direct methods employing the program SHELXS-97 [5]. The structure was refined by SHELXL-97 [5]. Crystallographic details are summarized in Table 1. Atomic coordinates and equivalent atomic displacement parameters, with their standard deviations are given in Table 2. Selected interatomic distances are provided in Table 3.

Table 1 Data collection and structure refinement parameters for Ce3Pt4Al6.

Space group

Pnma

Lattice parameters

a = 13.6589(2) A

 

b = 4.3331(1) A

Cell volume (A3)

c = 17.4740(3) A

 

1034.21(3)

Formula per unit cell

4

Calculated density (g/cm3)

8.751

Scan range (degrees)

2.33<9<31.00

Linear absorption coefficient

67.249

(mm-1)

 

Range in hkl

-19 < h < 19

 

-6 < k < 6

 

-24 < l < 25

Symmetry-independent

1845

reflections

 

Reflections with I>2o(I)

1793

Number of refined

80

parameters

 

Goodness of fit

1.114

R

0.049

 

0.149

Table 2 Atomic coordinates and equivalent isotropic displacement parameters of Ce3Pt4Al6a

Atom

Wyckoff site

x

y

z

Ueq (A2)

Ce1

4c

0.07521(7)

1/4

0.84864(5)

0.0085(2)

Ce2

4c

0.30248(7)

1/4

0.03267(5)

0.0080(2)

Ce3

4c

0.36757(7)

1/4

0.80618(5)

0.0083(2)

Pt1

4c

0.07161(5)

1/4

0.42837(4)

0.0079(2)

Pt2

4c

0.08973(5)

1/4

0.18707(4)

0.0112(2)

Pt3

4c

0.14853(4)

1/4

0.67761(4)

0.0075(2)

Pt4

4c

0.37790(4)

1/4

0.49254(4)

0.0086(2)

Al1

4c

0.0265(4)

1/4

0.5669(3)

0.0082(9)

Al2

4c

0.0562(4)

1/4

0.0437(3)

0.0097(9)

Al3

4c

0.2507(4)

1/4

0.3963(4)

0.0123(10)

Al4

4c

0.2721(4)

1/4

0.2281(3)

0.0082(9)

Al5

4c

0.3277(4)

1/4

0.6306(3)

0.0077(9)

Al6

4c

0.4605(4)

1/4

0.1915(3)

0.0085(9)

a The structure was refined with anisotropic displacement parameters for all atoms. The positional parameters were standardized using the program STRUCTURE TIDY [6].

3. Crystal structure description

The structure of Ce3Pt4Al6 shows ordered occupation of all crystallographic sites. It is built of two identical atom layers of six-, five-, four- and three-membered rings at heights y = 1/4 and y = 3/4 (Fig. 1), related by inversion centers at y = 0 and y = 1/2. The Ce1 and Ce2 atoms are situated at the centers of hexagonal prisms with three and four additional atoms, respectively (Fig. 2a). The Ce3 atom is at the center of a pentagonal prism with two additional atoms.

Fig. 1 Projection of the structure of Ce3Pt4Al6 on the XZ-plane. Light grey circles correspond to cerium atoms, dark grey circles to platinum atoms, and white circles to aluminum atoms. All atoms lie in the mirror planes at y = 1/4 (dashed lines) and y = 3/4 (solid lines).

b

Fig. 2 Coordination polyhedra in the structures of Ce3Pt4Al6 (a) and Y3Pt4Ge6 (b).

a

Table 3 Interatomic distances in Ce3Pt4Al6.

Atom

To atom

d, A

Atom

To atom

d, A

Ce1

Pt3

3.1519(11)

 

2 Ce2

3.3550(8)

 

2 Pt2

3.18.72(8)

 

2 Ce1

3.3804(9)

 

2 Al3

3.322(4)

 

 

 

 

2 Pt4

3.3804(9)

Al1

Pt1

2.498(5)

 

2 Al2

3.385(4)

 

2Pt1

2.549(3)

 

Al5

3.401(5)

 

Pt3

2.554(5)

 

Al2

3.418(5)

 

2 Al6

3.077(5)

 

2 Al6

3.531(4)

 

Ce3

3.103(5)

 

2 Al4

3.671(4)

 

2 Ce2

3.242(4)

 

 

 

 

2 Al1

3.269(8)

Ce2

2 Al1

3.242(4)

 

Ce2

3.519(5)

 

2 Al5

3.283(4)

 

 

 

 

2 Al3

3.302(5)

Al2

2 Pt4

2.511(3)

 

2 Pt1

3.3126(8)

 

Pt4

2.517(6)

 

2 Pt4

3.3550(8)

 

Pt2

2.547(5)

 

Al2

3.369(6)

 

2 Al2

3.064(8)

 

2 Pt3

3.3995(9)

 

2 Al5

3.084(5)

 

Al4

3.441(5)

 

Ce2

3.369(5)

 

Al6

3.516(5)

 

2 Ce1

3.385(4)

 

Al1

3.519(5)

 

Ce1

3.418(5)

Ce3

2 Pt2

3.0603(8)

Al3

Pt4

2.418(6)

 

Al1

3.103(5)

 

Pt1

2.510(6)

 

Al5

3.117(5)

 

Al4

2.952(8)

 

2 Al3

3.128(4)

 

2 Ce3

3.128(4)

 

2 Pt1

3.1532(8)

 

2 Ce2

3.302(5)

 

2 Al4

3.193(4)

 

2 Ce1

3.322(4)

 

2 Al6

3.195(4)

 

 

 

 

 

 

Al4

2 Pt3

2.579(3)

Pt1

Al1

2.498(5)

 

Pt2

2.592(5)

 

Al3

2.510(6)

 

Al6

2.652(7)

 

2 Al1

2.549(3)

 

Al3

2.952(8)

 

Al6

2.587(5)

 

2 Al5

3.075(5)

 

2 Ce3

3.1532(8)

 

2 Ce3

3.193(4)

 

2 Ce2

3.3126(8)

 

Ce2

3.441(5)

 

 

 

 

2 Ce1

3.671(4)

Pt2

Al2

2.547(5)

 

 

 

 

Al4

2.592(5)

Al5

Pt4

2.508(5)

 

2 Al5

2.635(3)

 

Pt3

2.581(5)

 

Al6

2.760(5)

 

2 Pt2

2.635(3)

 

2 Ce3

3.0603(8)

 

2 Al4

3.075(5)

 

2 Ce1

3.1872(8)

 

2 Al2

3.084(5)

 

 

 

 

Ce3

3.117(5)

Pt3

Al1

2.554(5)

 

2 Ce2

3.283(4)

 

2 Al4

2.579(3)

 

Ce1

3.401(5)

 

Al5

2.581(5)

 

 

 

 

2 Al6

2.640(3)

Al6

Pt1

2.587(5)

 

Ce1

3.1519(11)

 

2 Pt3

2.640(3)

 

2 Ce2

3.3995(9)

 

Al4

2.652(7)

 

 

 

 

Pt2

2.760(5)

Pt4

Al3

2.418(6)

 

2 Al1

3.077(5)

 

Al5

2.508(5)

 

2 Ce3

3.195(4)

 

2 Al2

2.511(3)

 

Ce2

3.516(5)

 

Al2

2.517(6)

 

2 Ce1

3.531(4)

A.I. Tursina et al., Crystal structure of the novel compound Ce3Pt4Al6 Table 4 Coordination polyhedra in the structures of Ce3Pt4Al6 and Y3Pt4Ge6 [4].

Atom and its

CN

Polyhedron

Atom and its

CN

Polyhedron

neighbors

 

 

neighbors

 

 

Ce1[Pt5Al10]

15

Hexagonal prism with 3 additional atoms

Y1[Pt6Ge9]

15

Hexagonal prism with 3 additional atoms

Ce2[Pt6Al10]

16

Hexagonal prism with 4 additional atoms

Y2[Pt6Ge9]

15

Hexagonal prism with 3 additional atoms

Ce3[Pt4Al8]

12

Pentagonal prism with 2 additional atoms

Y3[Pt6Ge8]

14

Pentagonal prism with 4 additional atoms

Pt1[Ce4Al5]

9

Trigonal prism with 3 additional atoms

Pt1[Y4Ge5]

9

Trigonal prism with 3 additional atoms

Pt2[Ce4Al5]

9

Trigonal prism with 3 additional atoms

Pt2[Y5Ge5]

10

Trigonal prism with 4 additional atoms

Pt3[Ce3Al6]

9

Trigonal prism with 3 additional atoms

Pt3[Y4Ge5]

9

Trigonal prism with 3 additional atoms

Pt4[Ce4Al5]

9

Trigonal prism with 3 additional atoms

Pt4[Y5Ge5]

10

Trigonal prism with 4 additional atoms

Al1[Ce4Pt4Al4]

12

Tetragonal prism with 4 additional atoms

Ge1[Y4Pt4Ge4]

12

Tetragonal prism with 4 additional atoms

Al2[Ce4Pt4Al4]

12

Tetragonal prism with 4 additional atoms

Ge2[Y4Pt4Ge4]

12

Tetragonal prism with 4 additional atoms

Al3[Ce6Pt2Al1]

9

Trigonal prism with 3 additional atoms

Ge3[Y6Pt3]

9

Trigonal prism with 3 additional atoms

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