research papers
The crystal structure of silicalite (SiO2) with a substantial amount of structural hydroxyl groups [Si(1−x)O(2−4x)(OH)4x, with 0.08 < x < 0.10] has been refined from neutron powder diffraction data measured using the HRPD instrument at the ISIS pulsed neutron source. Powder data were collected on the as-synthesized orthorhombic sample at 298 K, and on the deuterated monoclinic sample at 100 K. Preferential location of Si-atom vacancies was found on four out of 12 independent T sites in the orthorhombic silicalite [Si(6), Si(7), Si(10) and Si(11)], although the H atoms of the substituting hydroxyl groups could not be located because of the low statistical site occupancy on multiple sites. No significant population of D atoms or of Si vacancies was found in the tetrahedral sites of the monoclinic sample. The detected long-range order of adjacent Si atoms in defective orthorhombic [MFI] structures is compatible with a mechanism of Si vacancy clustering and with the model of hydroxyl nests assumed in the literature on the basis of IR spectroscopic evidence. Crystal data: orthorhombic, Pnma, Z = 8, a = 20.0511 (1), b = 19.8757 (1), c = 13.36823 (9) Å, V = 5327.62 (5) Å3, Dx = 1.798 g cm−3, Mr = 721.01; monoclinic, P21/n, Z = 4, a = 19.8352 (2), b = 20.0903 (2), c = 13.3588 (1) Å, β = 90.892 (1)°, V = 5322.78 (6) Å3, Dx = 1.799 g cm−3, Mr = 1442.02.
Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768199008927/na0094sup1.cif | |
Text file https://doi.org/10.1107/S0108768199008927/na0094Isup2.txt | |
Text file https://doi.org/10.1107/S0108768199008927/na0094IIsup3.txt | |
Text file https://doi.org/10.1107/S0108768199008927/na0094sup4.txt |
Computing details top
(I) top
Crystal data top
H3.6O24Si11.04 | c = 13.36823 (9) Å |
Mr = 721.01 | V = 5327.62 (5) Å3 |
Orthorhombic, Pnma | Z = 8 |
Hall symbol: -P 2ac 2n | Dx = 1.798 Mg m−3 |
a = 20.0511 (1) Å | Neutron radiation, λ = 1.22 Å |
b = 19.8757 (1) Å |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | ||
Si(1) | 0.4245 (3) | 0.0601 (3) | −0.3315 (4) | 0.0256 (4) | |
Si(2) | 0.3083 (3) | 0.0281 (2) | −0.1860 (4) | 0.0256 (4) | |
Si(3) | 0.2779 (3) | 0.0612 (3) | 0.0341 (4) | 0.0256 (4) | |
Si(4) | 0.1182 (3) | 0.0628 (3) | 0.0283 (4) | 0.0256 (4) | |
Si(5) | 0.0749 (3) | 0.0289 (3) | −0.1874 (5) | 0.0256 (4) | |
Si(6) | 0.1888 (3) | 0.0607 (3) | −0.3272 (4) | 0.0256 (4) | |
Si(7) | 0.4249 (3) | −0.1723 (2) | −0.3265 (4) | 0.0256 (4) | |
Si(8) | 0.3087 (3) | −0.1321 (3) | −0.1842 (4) | 0.0256 (4) | |
Si(9) | 0.2721 (3) | −0.1754 (2) | 0.0335 (4) | 0.0256 (4) | |
Si(10) | 0.1199 (3) | −0.1738 (2) | 0.0320 (4) | 0.0256 (4) | |
Si(11) | 0.0723 (3) | −0.1292 (3) | −0.1809 (5) | 0.0256 (4) | |
Si(12) | 0.1858 (3) | −0.1732 (2) | −0.3233 (4) | 0.0256 (4) | |
O(1) | 0.3777 (3) | 0.0495 (5) | −0.2359 (5) | 0.0408 (4) | |
O(2) | 0.3060 (5) | 0.0631 (4) | −0.0782 (4) | 0.0408 (4) | |
O(3) | 0.1981 (3) | 0.0601 (4) | 0.0274 (4) | 0.0408 (4) | |
O(4) | 0.0989 (3) | 0.0663 (4) | −0.0876 (4) | 0.0408 (4) | |
O(5) | 0.1161 (3) | 0.0616 (5) | −0.2776 (5) | 0.0408 (4) | |
O(6) | 0.2487 (3) | 0.0618 (5) | −0.2482 (5) | 0.0408 (4) | |
O(7) | 0.3745 (4) | −0.1628 (4) | −0.2343 (6) | 0.0408 (4) | |
O(8) | 0.3077 (5) | −0.1545 (3) | −0.0694 (4) | 0.0408 (4) | |
O(9) | 0.1963 (3) | −0.1505 (3) | 0.0227 (5) | 0.0408 (4) | |
O(10) | 0.0876 (4) | −0.1665 (4) | −0.0772 (5) | 0.0408 (4) | |
O(11) | 0.1152 (3) | −0.1546 (4) | −0.2746 (6) | 0.0408 (4) | |
O(12) | 0.2437 (4) | −0.1531 (4) | −0.2462 (6) | 0.0408 (4) | |
O(13) | 0.3153 (4) | −0.0521 (2) | −0.1876 (4) | 0.0408 (4) | |
O(14) | 0.0840 (3) | −0.0501 (3) | −0.1678 (5) | 0.0408 (4) | |
O(15) | 0.4193 (4) | 0.1321 (4) | −0.3842 (6) | 0.0408 (4) | |
O(16) | 0.4054 (4) | 0.0006 (4) | −0.4069 (6) | 0.0408 (4) | |
O(17) | 0.4014 (4) | −0.1346 (4) | −0.4264 (6) | 0.0408 (4) | |
O(18) | 0.1906 (5) | 0.1319 (3) | −0.3828 (5) | 0.0408 (4) | |
O(19) | 0.1899 (5) | 0.0019 (3) | −0.4089 (5) | 0.0408 (4) | |
O(20) | 0.1959 (6) | −0.1323 (3) | −0.4251 (4) | 0.0408 (4) | |
O(21) | −0.0021 (3) | 0.0441 (4) | −0.2093 (5) | 0.0408 (4) | |
O(22) | −0.0019 (3) | −0.1513 (5) | −0.2103 (6) | 0.0408 (4) | |
O(23) | 0.4287 (7) | −0.25 | −0.3573 (9) | 0.0408 (4) | |
O(24) | 0.2025 (6) | −0.25 | −0.3473 (8) | 0.0408 (4) | |
O(25) | 0.2881 (6) | −0.25 | 0.0722 (7) | 0.0408 (4) | |
O(26) | 0.1136 (7) | −0.25 | 0.0696 (9) | 0.0408 (4) |
Bond lengths (Å) top
Si(1)—O(1/15/16) | 1.600 (2) | Si(7)—O(7/17/23) | 1.602 (2) |
Si(2)—O(1/2/6) | 1.601 (2) | Si(8)—O(8/12/13) | 1.599 (2) |
Si(3)—O(2/3) | 1.603 (2) | Si(9)—O(8/9/25) | 1.603 (2) |
Si(4)—O(3/4) | 1.600 (2) | Si(10)—O(9/10/26) | 1.602 (2) |
Si(5)—O(5/14/21) | 1.601 (2) | Si(11)—O(10/11/14/22) | 1.601 (2) |
Si(6)—O(5/6/18/19) | 1.600 (2) | Si(12)—O(11/12/20/24) | 1.600 (2) |
(II) top
Crystal data top
H3.6O24Si11.04 | c = 13.3588 (1) Å |
Mr = 1442.02 | β = 90.892 (1)° |
Monoclinic, P21/n | V = 5322.78 (6) Å3 |
Hall symbol: -P 2yn | Z = 4 |
a = 19.8352 (2) Å | Dx = 1.799 Mg m−3 |
b = 20.0903 (2) Å | Neutron radiation, λ = 1.22 Å |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | ||
Si(1) | 0.0622 (4) | 0.4223 (4) | −0.3282 (6) | 0.0114 (5) | |
Si(2) | 0.0329 (4) | 0.3195 (4) | −0.1641 (5) | 0.0114 (5) | |
Si(3) | 0.0605 (4) | 0.2820 (4) | 0.0600 (5) | 0.0114 (5) | |
Si(4) | 0.0628 (4) | 0.1253 (4) | 0.0358 (7) | 0.0114 (5) | |
Si(5) | 0.0307 (4) | 0.0781 (4) | −0.1760 (6) | 0.0114 (5) | |
Si(6) | 0.0546 (4) | 0.2006 (4) | −0.3115 (5) | 0.0114 (5) | |
Si(7) | −0.1737 (4) | 0.4250 (4) | −0.3190 (6) | 0.0114 (5) | |
Si(8) | −0.1250 (4) | 0.3098 (4) | −0.1726 (6) | 0.0114 (5) | |
Si(9) | −0.1782 (4) | 0.2730 (4) | 0.0389 (5) | 0.0114 (5) | |
Si(10) | −0.1777 (4) | 0.1193 (5) | 0.0334 (6) | 0.0114 (5) | |
Si(11) | −0.1267 (4) | 0.0715 (4) | −0.1714 (6) | 0.0114 (5) | |
Si(12) | −0.1596 (3) | 0.1897 (4) | −0.3167 (6) | 0.0114 (5) | |
Si(13) | 0.4458 (4) | 0.4303 (4) | −0.3369 (6) | 0.0114 (5) | |
Si(14) | 0.4775 (4) | 0.3144 (4) | −0.1889 (6) | 0.0114 (5) | |
Si(15) | 0.4395 (4) | 0.2742 (4) | 0.0222 (5) | 0.0114 (5) | |
Si(16) | 0.4358 (4) | 0.1202 (4) | 0.0417 (6) | 0.0114 (5) | |
Si(17) | 0.4739 (4) | 0.0732 (5) | −0.1745 (6) | 0.0114 (5) | |
Si(18) | 0.4365 (3) | 0.1871 (4) | −0.3115 (6) | 0.0114 (5) | |
Si(19) | 0.6710 (4) | 0.4237 (4) | −0.3098 (6) | 0.0114 (5) | |
Si(20) | 0.6341 (4) | 0.3099 (4) | −0.1709 (6) | 0.0114 (5) | |
Si(21) | 0.6646 (4) | 0.2738 (4) | 0.0454 (6) | 0.0114 (5) | |
Si(22) | 0.6685 (4) | 0.1203 (4) | 0.0347 (6) | 0.0114 (5) | |
Si(23) | 0.6333 (4) | 0.0714 (4) | −0.1818 (6) | 0.0114 (5) | |
Si(24) | 0.6840 (3) | 0.1956 (4) | −0.2963 (5) | 0.0114 (5) | |
O(1) | 0.0619 (6) | 0.3829 (5) | −0.2232 (8) | 0.0134 (4) | |
O(2) | 0.0636 (5) | 0.3100 (7) | −0.0528 (5) | 0.0134 (4) | |
O(3) | 0.0470 (5) | 0.2036 (4) | 0.0447 (8) | 0.0134 (4) | |
O(4) | 0.0718 (6) | 0.1068 (6) | −0.0806 (7) | 0.0134 (4) | |
O(5) | 0.0444 (6) | 0.1260 (5) | −0.2700 (8) | 0.0134 (4) | |
O(6) | 0.0519 (6) | 0.2500 (5) | −0.2169 (8) | 0.0134 (4) | |
O(7) | −0.1567 (6) | 0.3732 (5) | −0.2300 (8) | 0.0134 (4) | |
O(8) | −0.1703 (5) | 0.2947 (6) | −0.0763 (6) | 0.0134 (4) | |
O(9) | −0.1555 (5) | 0.1963 (4) | 0.0302 (8) | 0.0134 (4) | |
O(10) | −0.1741 (6) | 0.0909 (6) | −0.0791 (7) | 0.0134 (4) | |
O(11) | −0.1511 (6) | 0.1184 (5) | −0.2627 (7) | 0.0134 (4) | |
O(12) | −0.1264 (6) | 0.2472 (5) | −0.2479 (8) | 0.0134 (4) | |
O(13) | −0.0470 (4) | 0.3236 (6) | −0.1450 (8) | 0.0134 (4) | |
O(14) | −0.0479 (4) | 0.0859 (6) | −0.1505 (9) | 0.0134 (4) | |
O(15) | 0.1359 (4) | 0.4230 (5) | −0.3771 (7) | 0.0134 (4) | |
O(16) | −0.0015 (5) | 0.3862 (6) | −0.3810 (7) | 0.0134 (4) | |
O(17) | −0.1352 (5) | 0.4090 (6) | −0.4215 (7) | 0.0134 (4) | |
O(18) | 0.1308 (4) | 0.2066 (6) | −0.3499 (7) | 0.0134 (4) | |
O(19) | 0.0025 (5) | 0.2116 (6) | −0.4035 (7) | 0.0134 (4) | |
O(20) | −0.1256 (4) | 0.1944 (7) | −0.4251 (7) | 0.0134 (4) | |
O(21) | 0.0486 (6) | 0.0036 (4) | −0.2113 (9) | 0.0134 (4) | |
O(22) | −0.1425 (6) | −0.0026 (4) | −0.2111 (8) | 0.0134 (4) | |
O(23) | −0.2526 (4) | 0.4293 (6) | −0.3478 (8) | 0.0134 (4) | |
O(24) | −0.2391 (3) | 0.2036 (6) | −0.3310 (8) | 0.0134 (4) | |
O(25) | −0.2560 (4) | 0.2763 (6) | 0.0710 (8) | 0.0134 (4) | |
O(26) | −0.2541 (4) | 0.1160 (7) | 0.0721 (8) | 0.0134 (4) | |
O(27) | 0.4592 (6) | 0.3852 (5) | −0.2389 (7) | 0.0134 (4) | |
O(28) | 0.4584 (5) | 0.3196 (5) | −0.0725 (6) | 0.0134 (4) | |
O(29) | 0.4292 (5) | 0.1957 (4) | 0.0025 (8) | 0.0134 (4) | |
O(30) | 0.4461 (6) | 0.0820 (6) | −0.0628 (6) | 0.0134 (4) | |
O(31) | 0.4288 (5) | 0.1200 (5) | −0.2468 (8) | 0.0134 (4) | |
O(32) | 0.4405 (6) | 0.2513 (5) | −0.2394 (9) | 0.0134 (4) | |
O(33) | 0.6676 (6) | 0.3775 (5) | −0.2115 (7) | 0.0134 (4) | |
O(34) | 0.6418 (5) | 0.3167 (5) | −0.0512 (6) | 0.0134 (4) | |
O(35) | 0.6441 (5) | 0.1967 (4) | 0.0315 (7) | 0.0134 (4) | |
O(36) | 0.6588 (6) | 0.0785 (6) | −0.0673 (6) | 0.0134 (4) | |
O(37) | 0.6726 (6) | 0.1212 (5) | −0.2551 (8) | 0.0134 (4) | |
O(38) | 0.6750 (6) | 0.2439 (5) | −0.2013 (8) | 0.0134 (4) | |
O(39) | 0.5562 (3) | 0.2969 (6) | −0.2002 (8) | 0.0134 (4) | |
O(40) | 0.5536 (4) | 0.0868 (6) | −0.1830 (9) | 0.0134 (4) | |
O(41) | 0.3761 (5) | 0.4211 (6) | −0.3987 (8) | 0.0134 (4) | |
O(42) | 0.5025 (5) | 0.4190 (6) | −0.4199 (7) | 0.0134 (4) | |
O(43) | 0.6317 (5) | 0.3909 (6) | −0.4040 (8) | 0.0134 (4) | |
O(44) | 0.3669 (4) | 0.1925 (7) | −0.3744 (7) | 0.0134 (4) | |
O(45) | 0.5021 (4) | 0.1801 (5) | −0.3802 (6) | 0.0134 (4) | |
O(46) | 0.6346 (5) | 0.2119 (6) | −0.3899 (7) | 0.0134 (4) | |
O(47) | 0.4625 (6) | −0.0041 (5) | −0.2021 (8) | 0.0134 (4) | |
O(48) | 0.6448 (6) | −0.0041 (4) | −0.2182 (9) | 0.0134 (4) |
Bond lengths (Å) top
Si(1)—O(1/15/16) | 1.611 (1) | Si(13)—O(27/41/42) | 1.610 (1) |
Si(2)—O(1/2/6/13) | 1.610 (1) | Si(14)—O(27/28/32/39) | 1.609 (1) |
Si(3)—O(2/3) | 1.609 (1) | Si(15)—O(29/29) | 1.609 (1) |
Si(4)—O(3/4) | 1.610 (1) | Si(16)—O(29/30) | 1.609 (1) |
Si(5)—O(4/5/14/21) | 1.609 (1) | Si(17)—O(30/31) | 1.610 (1) |
Si(6)—O(5/6/18/19) | 1.610 (1) | Si(18)—O(31/32/44/45) | 1.609 (1) |
Si(7)—O(7/17/23) | 1.610 (1) | Si(19)—O(33/43) | 1.610 (1) |
Si(8)—O(7/8/12/13) | 1.609 (1) | Si(20)—O(33/34/38/39) | 1.609 (1) |
Si(9)—O(8/9/25) | 1.610 (1) | Si(21)—O(34/35) | 1.610 (1) |
Si(10)—O(9/10/26) | 1.610 (1) | Si(22)—O(35/36) | 1.610 (1) |
Si(11)—O(10/11/14) | 1.610 (1) | Si(23)—O(36/37/40/48) | 1.610 (1) |
Si(12)—O(11/12/20/24) | 1.610 (1) | Si(24)—O(27/38/46) | 1.610 (1) |