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The preparation and crystal structures of americium dichloride and dibromide
.L iplorg, nucl. Chem., 1973. Vol. 35, pp. 483-487.
THE OF
PREPARATION AMERICIUM
Pergamon Press.
AND
Printed in Great Britain
CRYSTAL
DICHLORIDE
AND
STRUCTURES DIBROMIDE*
R. D. BAYBARZ Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
(Received 11 April 1972) A b s t r a c t - T h e preparation and identification of two divalent americium compounds, AmClz and AmBr~, are reported. Lattice constants for the orthorhombic AmCI2 are ao = 8-963 _ 0.008, b = 7.573 --0.008 and c = 4.532 +__0.006/~. The lattice constants for the tetragonal AmBr2 are ao = 11.592 -+ 0.004 and c = 7.121 ___0.003 ,~. INTRODUCTION
THE RECENT preparation and identification of a divalent americium compound, AmI2[1], has given solid evidence for the accessibility of the divalent state of americium. This paper reports the preparation and identification of two additional divalent americium halide compounds. EXPERIMENTAL The dichloride and dibromide were prepared by the reaction of americium metal with mercuric halides as previously reported[I, 2] for AmI2 and for Tml2. The americium-243 metal was from the same source as reported in Ref.[l]. The americium metal was weighed in an argon atmosphere glove box and positioned in a quartz tube. The HgCl2 and HgBr2 were reagent grade. The quantity of mercury halide needed for the formation of americium dihalide was 1.12 mg HgCl2 and 1-48 mg HgBr2 per mg Am °. These quantities were weighed out and positioned in the quartz tubes. The mercury halides were then vacuum sublimed onto the americium metal and the tubes were evacuated to 1 x l 0 -~ Torr and sealed. The quartz tubes containing the reactants were heated in a furnace at 300°C for 4 days, then the Hg ° was sublimed to the opposite end of the tube and sealed off. The portion of the tube containing the americium halide was then reheated in the furnace at 400°C for l0 days. The quartz ampules were opened in an argon atmosphere glove box and X-ray samples were prepared. The samples were examined by standard X-ray techniques as reported in Ref. [l]. The error limits are one standard deviation. RESULTS AND DISCUSSION
The americium dichloride sample was a black granular product with a very small amount of light grey fine powder present. The types of materials were separated manually and examined separately by X-ray diffraction pattern. The light grey material was identified as AmCl3 on the basis of the diffraction pattern. The black granular material gave a completely different powder diffraction pattern which could be indexed on the basis of an orthorhombic cell. The lattice parameters for the black AmC12 are ao = 8.963-+-0.008, b = 7.573___0-008 and c = *Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation. 1. R. D. Baybarz, L. B. Asprey, C. E. Strouse and E. Fukushima, J. inorg, nucl. Chem. 34, 3427 (1972). 2. L.B. Asprey and F. H. Kruse, J. inorg, nucl. chem. 13, 32 (1960). 483
484
R . D . BAYBARZ Table I. Line list and indexing for americium dichloride 20(deg)
Line intensity
hkl
Observed
Calculated*
101 210 020 Ill 220 121 301 311 002 400 230 131 321 212] 022[ 420J 040 331 232 412 341 422~ 610J
22.20 23-10 23.50 25.20 31.10 32.50 36.10 38.00 39.70 40.30 41.20 42"50 43'40
22.09 23.17 23.60 25-07 31.02 32.50 36-11 38.08 39.88 40.35 41.14 42'30 43"54 46"58 46"82 47"23 48" 16 51"60 58"57 59"36 61"58 63"42 63"56
113]J 042~ 440 250 151
46"90 48"20 51"70 58:50 59"30 61"60 63"30
Observedt M M W S T M W W F F W W W W(b) T T F T T F
65.10 66.00
63.76 64.18 64"52 65.09 65.94
T T
123J
67.60
67.67
F(b)
612~ 701J 252 721
77.70
64-10
78.90 82-50
77.54 79.06 82"36
W(b)
Calculated* 57 112 54 I00 3 78 43 30 28 19 37 34 39 {34 17 17 9 8 24 1 9 {1~ [i 7 11
F(b) T T
8 5
*Calculated using the lattice parameter refinement program LCR-2[4] with ao = 8.9634, b - 7.5729 and c = 4.5319; with k(~)= 1.54178A and using th¢ Nelson-Riley extrapolation function. tEstimated relative intensity on basis of stron~g(S), medium (M), weak(W), faint(F) and trace(T). (b) denotes a broad line ~tCalculated using the POWD intensity program[5] utilizing the atomic coordinates and temperature coefficients of E u C I 2 [3], no absorption correction, and scaled such that the 111 line equals 100. 3. H. Biirnighausen, H. P. Beck and H. W. Grueninger, 9th Rare Earth Research Conference Blacksburg, Virginia, CONF-711001, 74-83 (October, 1971). 4. D. E. Williams, Ames Lab. Rept., IS-1052 (1964). 5. D.K. Smith, University of California Lawrence Radiation Lab. Rept., UCRL-7196 (1963).
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486
R. D. BAYBARZ Table 2. (contd)
20 (deg.) h k
l
7 4 33} 8 1 6 4 4 10 2 0 10
O ~}
8 6 85 36} 3 3 7 2 _]5 10 3 2, 9 6 lJ 11
8 7 8 6 5 8 10
0
6 4 1 0 4 7 2 10 6 4 1 6 4
~}
i} ~} i}
77.50 80.60 85.50 88.70 90.00 93"40 95-60 99.20 102-30 107.40
6
5 7 3 i} 9 7 11 3
10
Observed
108.80 111.00
Calculated*
77.69 77-69 80.55 85.50 88.84 88.84 89.97 90.19 93'19 93.41 93.45 95.48 95-57 99.32 99.32 99.37 101.95 102.25 107.25 107-38 107.41 107.73 108.57 110.96 111.27 111.27
Line intensity ObservedT
F T T F F F T T T F(b)
T F(b)
Calculated~:
{0.7 1.6 1.5 0.9 {3"0 0.3 {2"3 1"2 [0-7 10"6 0.3 {1.2 0.2 {0.5 1.1 0.4 {0.5 0.2 {0.7 1.4 1.5 2.2 0.3 {1.5 0.2 0.2
*Calculated using the lattice parameter refinement program LCR2[4] with ao= 11.5819A, c = 7 . 1 2 0 9 A and h = 1.54178A, and using the Nelson-Riley extrapolation function. fEstimated relative intensities on basis of strong(S), medium(M), weak(W), faint(F) and trace(T). (b) denotes a broad fine. ~Calculated using the POWD intensity program[5] utilizing the atomic coordinates and temperature coefficients of EuBr~[3], no absorption correction, and scaled such that the intensities of the 211 and 121 lines summed to 100.
4.532-----0"006 A. The AmCI2 is isostructural with PbC12 and EuCI2[3]. A theoretical powder pattern calculated using the EuCI2 structure [3] gave satisfactory agreement between observed and calculated intensities. A line list and indexing for AmC12 is given in Table 1. The preparation had a slightly greater amount of chloride present than was needed for the AmCI~ reaction, and as a result a small amount of AmC13 was formed. Since both reaction products coexisted in the quartz tube, the existence of divalent americium as a true valence state was verified in this experiment. The americium dibromide sample was also a black granular product. X-ray powder diffraction analysis indicated that the sample is isostructural with EuBr2
The preparation and crystalstructuresof americiumdichlorideand dibromide
487
[3]. The lattice parameters for the tetragonal cell are ao = 11.592 ___0-004 and c = 7.121 ___0.003 A. A line list and indexing for the black AmBr2 is given in Table 2. The nature of this tetragonal cell is such that at angles greater than -~ 45 ° in 20, the intensities of the reflections, are very weak. In spite of the very weak reflections at high angle, 57 lines were read and indexed; however, it was not possible to determine the high angle center and thus to correct for film shrinkage. In an attempt to have both AmBr2 and AmBr3 products present in the reaction tube, an experiment was made in which sufficient HgBr2 was present to give approximately equal quantities of both materials. The resultant product was homogeneous and of a brown color. X-ray diffraction analysis indicated that it was neither AmBr2 or AmBr3 but it exhibited a different structure. This powder pattern, however, was identical with that obtained from intermediate product resulting from only partial hydrogen reduction of CfBr3[6]. Apparently a stable phase of mixed valence states of the metal is present in the bromide system. The crystal structure and stoichiometry of this intermediate phase is being further investigated. The americium dichloride and dibromide samples were stable in argon at room temperature, and the X-ray patterns showed no deterioration over a 4 week time period. The lattice parameters for the two Am dihalides are slightly greater than those reported for the similar Eu compounds, as would be expected from the ionic radius trend observed for the corresponding trivalent ions.
THE OF
PREPARATION AMERICIUM
Pergamon Press.
AND
Printed in Great Britain
CRYSTAL
DICHLORIDE
AND
STRUCTURES DIBROMIDE*
R. D. BAYBARZ Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
(Received 11 April 1972) A b s t r a c t - T h e preparation and identification of two divalent americium compounds, AmClz and AmBr~, are reported. Lattice constants for the orthorhombic AmCI2 are ao = 8-963 _ 0.008, b = 7.573 --0.008 and c = 4.532 +__0.006/~. The lattice constants for the tetragonal AmBr2 are ao = 11.592 -+ 0.004 and c = 7.121 ___0.003 ,~. INTRODUCTION
THE RECENT preparation and identification of a divalent americium compound, AmI2[1], has given solid evidence for the accessibility of the divalent state of americium. This paper reports the preparation and identification of two additional divalent americium halide compounds. EXPERIMENTAL The dichloride and dibromide were prepared by the reaction of americium metal with mercuric halides as previously reported[I, 2] for AmI2 and for Tml2. The americium-243 metal was from the same source as reported in Ref.[l]. The americium metal was weighed in an argon atmosphere glove box and positioned in a quartz tube. The HgCl2 and HgBr2 were reagent grade. The quantity of mercury halide needed for the formation of americium dihalide was 1.12 mg HgCl2 and 1-48 mg HgBr2 per mg Am °. These quantities were weighed out and positioned in the quartz tubes. The mercury halides were then vacuum sublimed onto the americium metal and the tubes were evacuated to 1 x l 0 -~ Torr and sealed. The quartz tubes containing the reactants were heated in a furnace at 300°C for 4 days, then the Hg ° was sublimed to the opposite end of the tube and sealed off. The portion of the tube containing the americium halide was then reheated in the furnace at 400°C for l0 days. The quartz ampules were opened in an argon atmosphere glove box and X-ray samples were prepared. The samples were examined by standard X-ray techniques as reported in Ref. [l]. The error limits are one standard deviation. RESULTS AND DISCUSSION
The americium dichloride sample was a black granular product with a very small amount of light grey fine powder present. The types of materials were separated manually and examined separately by X-ray diffraction pattern. The light grey material was identified as AmCl3 on the basis of the diffraction pattern. The black granular material gave a completely different powder diffraction pattern which could be indexed on the basis of an orthorhombic cell. The lattice parameters for the black AmC12 are ao = 8.963-+-0.008, b = 7.573___0-008 and c = *Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation. 1. R. D. Baybarz, L. B. Asprey, C. E. Strouse and E. Fukushima, J. inorg, nucl. Chem. 34, 3427 (1972). 2. L.B. Asprey and F. H. Kruse, J. inorg, nucl. chem. 13, 32 (1960). 483
484
R . D . BAYBARZ Table I. Line list and indexing for americium dichloride 20(deg)
Line intensity
hkl
Observed
Calculated*
101 210 020 Ill 220 121 301 311 002 400 230 131 321 212] 022[ 420J 040 331 232 412 341 422~ 610J
22.20 23-10 23.50 25.20 31.10 32.50 36.10 38.00 39.70 40.30 41.20 42"50 43'40
22.09 23.17 23.60 25-07 31.02 32.50 36-11 38.08 39.88 40.35 41.14 42'30 43"54 46"58 46"82 47"23 48" 16 51"60 58"57 59"36 61"58 63"42 63"56
113]J 042~ 440 250 151
46"90 48"20 51"70 58:50 59"30 61"60 63"30
Observedt M M W S T M W W F F W W W W(b) T T F T T F
65.10 66.00
63.76 64.18 64"52 65.09 65.94
T T
123J
67.60
67.67
F(b)
612~ 701J 252 721
77.70
64-10
78.90 82-50
77.54 79.06 82"36
W(b)
Calculated* 57 112 54 I00 3 78 43 30 28 19 37 34 39 {34 17 17 9 8 24 1 9 {1~ [i 7 11
F(b) T T
8 5
*Calculated using the lattice parameter refinement program LCR-2[4] with ao = 8.9634, b - 7.5729 and c = 4.5319; with k(~)= 1.54178A and using th¢ Nelson-Riley extrapolation function. tEstimated relative intensity on basis of stron~g(S), medium (M), weak(W), faint(F) and trace(T). (b) denotes a broad line ~tCalculated using the POWD intensity program[5] utilizing the atomic coordinates and temperature coefficients of E u C I 2 [3], no absorption correction, and scaled such that the 111 line equals 100. 3. H. Biirnighausen, H. P. Beck and H. W. Grueninger, 9th Rare Earth Research Conference Blacksburg, Virginia, CONF-711001, 74-83 (October, 1971). 4. D. E. Williams, Ames Lab. Rept., IS-1052 (1964). 5. D.K. Smith, University of California Lawrence Radiation Lab. Rept., UCRL-7196 (1963).
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486
R. D. BAYBARZ Table 2. (contd)
20 (deg.) h k
l
7 4 33} 8 1 6 4 4 10 2 0 10
O ~}
8 6 85 36} 3 3 7 2 _]5 10 3 2, 9 6 lJ 11
8 7 8 6 5 8 10
0
6 4 1 0 4 7 2 10 6 4 1 6 4
~}
i} ~} i}
77.50 80.60 85.50 88.70 90.00 93"40 95-60 99.20 102-30 107.40
6
5 7 3 i} 9 7 11 3
10
Observed
108.80 111.00
Calculated*
77.69 77-69 80.55 85.50 88.84 88.84 89.97 90.19 93'19 93.41 93.45 95.48 95-57 99.32 99.32 99.37 101.95 102.25 107.25 107-38 107.41 107.73 108.57 110.96 111.27 111.27
Line intensity ObservedT
F T T F F F T T T F(b)
T F(b)
Calculated~:
{0.7 1.6 1.5 0.9 {3"0 0.3 {2"3 1"2 [0-7 10"6 0.3 {1.2 0.2 {0.5 1.1 0.4 {0.5 0.2 {0.7 1.4 1.5 2.2 0.3 {1.5 0.2 0.2
*Calculated using the lattice parameter refinement program LCR2[4] with ao= 11.5819A, c = 7 . 1 2 0 9 A and h = 1.54178A, and using the Nelson-Riley extrapolation function. fEstimated relative intensities on basis of strong(S), medium(M), weak(W), faint(F) and trace(T). (b) denotes a broad fine. ~Calculated using the POWD intensity program[5] utilizing the atomic coordinates and temperature coefficients of EuBr~[3], no absorption correction, and scaled such that the intensities of the 211 and 121 lines summed to 100.
4.532-----0"006 A. The AmCI2 is isostructural with PbC12 and EuCI2[3]. A theoretical powder pattern calculated using the EuCI2 structure [3] gave satisfactory agreement between observed and calculated intensities. A line list and indexing for AmC12 is given in Table 1. The preparation had a slightly greater amount of chloride present than was needed for the AmCI~ reaction, and as a result a small amount of AmC13 was formed. Since both reaction products coexisted in the quartz tube, the existence of divalent americium as a true valence state was verified in this experiment. The americium dibromide sample was also a black granular product. X-ray powder diffraction analysis indicated that the sample is isostructural with EuBr2
The preparation and crystalstructuresof americiumdichlorideand dibromide
487
[3]. The lattice parameters for the tetragonal cell are ao = 11.592 ___0-004 and c = 7.121 ___0.003 A. A line list and indexing for the black AmBr2 is given in Table 2. The nature of this tetragonal cell is such that at angles greater than -~ 45 ° in 20, the intensities of the reflections, are very weak. In spite of the very weak reflections at high angle, 57 lines were read and indexed; however, it was not possible to determine the high angle center and thus to correct for film shrinkage. In an attempt to have both AmBr2 and AmBr3 products present in the reaction tube, an experiment was made in which sufficient HgBr2 was present to give approximately equal quantities of both materials. The resultant product was homogeneous and of a brown color. X-ray diffraction analysis indicated that it was neither AmBr2 or AmBr3 but it exhibited a different structure. This powder pattern, however, was identical with that obtained from intermediate product resulting from only partial hydrogen reduction of CfBr3[6]. Apparently a stable phase of mixed valence states of the metal is present in the bromide system. The crystal structure and stoichiometry of this intermediate phase is being further investigated. The americium dichloride and dibromide samples were stable in argon at room temperature, and the X-ray patterns showed no deterioration over a 4 week time period. The lattice parameters for the two Am dihalides are slightly greater than those reported for the similar Eu compounds, as would be expected from the ionic radius trend observed for the corresponding trivalent ions.