Murti, G S R Krishna

English

IACS Institutional Repository

THE CRYSTAL STRUCTURE OF ANTHRACENE AT DIFFERENT TEMPERATURES*G. S. R . K R IS H N A  M U RTI()p n ('8  D kpartm bnt, I ndian  A ssociation foe the Oultivvtion of S< ien< f ,I  AD A VPU K, C A LCI»'W'A - 8 2(R e c e iv e d  ) o r  pu h livrtiion ^  J u m  Ui,Plate X IV54ABSTR AC T. Tht> crystal stnirturc ol unthraccno al -IHO C, 82 T, .Vj'C mid has been investigated by studying the Dcbyc-Sclierrpr patterns. Tt is found that at a tompmituro o f  about — J80°C the dimcmsions of the unit (‘(‘11 uiv given by u S.5t7 A.U., h •= 6.000 A.U., r =  J J .090 A.U. and P 125"'10'. Ttu>si> viilufs a, b ami r boiiiK slightly lower than those at the room temperature. Tht* im'an x^ alues of ao ami ar* the eo('ttieienis o f expansion along the three erystnllographie axes a ,  b and e respectively are lound to be 77.riXlO-«, 27..')2xl0-« and 31.05 s10-« respectively. The dimensions of the unit cell of the crystal at S0°0 are a =- K.696 A.U.. b ^  6.1.50 A.(h, e 11.3lt) A.U. ami /( 124'2S'.It appears that the eoeffieient o f expansion is low uplo about r.ri'C but a (enfold nieiease m the values takes place in the rnnae from .'.5  V  to 80' U. The values for a,„ «/, and a,, m the range from 32°0 to 80“C are 32.3.5 V |(l-;. 39 . 3 6 v l 0-.% and 27.45- 10  ^ respectively.I N 'I' K O O U 0 T I O NThe crystal structure o f  anthracene was first flctermined by Brag^j (Ib id ) by the X -ray  reflection method who observed that the crystal belongs to a space group C®2a with the unit cell d im ensions,«  =  S.58 A .U ., h = (j-(>2 A.U., r =  11.18 A .U . and /i  =  The space group was confirmed by Baiierjce (11)30) m tostudied the Debye-Scherrer patterns and the rotation photographs due to  t m crystal. The structure was determined more accurately by l .o>er<son ( . . .  em ploying the double Fourier series method and by  Mathieson Robertson ami Sinclair (1950) by the triple Fourier series method. These authors repoi e< ^  same space group for the crystal, but .slightly different unit cell dimensfons^ The values given by  them  are u ^  8..5fil A.U., 6 =. 6.0.36 A .U ., e 11.163 A .F . and =  124“ 42'.The mean values o f  coefficients o f  expansion a n , and *33 over the range ■20“ to  - 1 9 5 “C were reported by  Kozhin and KitaiGorodskii (1953) to  be 111.f X l0 -» ,  13 .4 X 1 0 -*  and 2 0 .3 x l0 - «  respectively. They reported the unit cell dim ensions at 20“ C as a =  8.544 A .U ., 6 =  6.023 A .U ., c -  11.14.J . • an(124“ 42 ' and a t - 1 9 5 “C as «  =  8.441 A .U ., h =  6.006 A .U .. c =  U .08  A .U .* Communicated by Prof. S. C. Sirkai.637538 G. 8. R. Krishna Murtift =  125^ 35'. So there is no change in the lattice o f  crystal in the tem perature range from  20 '0  to — 195°C.It is known now that the lattice o f  p-dichlorobenzene changes when the (crystal is heated to about 45'^C. It was thought worthwhile to find out whether the structure o f  anthracene remains unaltered or changes above room  tem pera­ture. The Debye-Scherrer pattern o f  the crystal was therefore studied at 55®C and 8(V^C and also at - 180°C in order to com pare with each other the structures at these temperatures.K X P K K I JVr E N T \ LAnthracene used was o f  chem ically pure quality supplied b y  J . T. Baker Chemical Co., U .S.A . The substance was powdered well in a m ortar and packed inside a glass tube o f  diam eter 0.7 mm and the Debye-Scherrcr pattern was photo- graph ei at different temperahire.s. The m ethods for keeping the pow der at the tem perature o f  liquid oxygen  and also at tem peratures higher than 32®0 were the same as those described by Krishna Murti and Sen (1956).A Seifert X -ra y  tube running at 2fi ma, 32 kV was used to  photograph the patterns. An exposure o f  about hrs was sufficient to get the pattern recorded with m oderate density. The rings obtained were sharp since the diam eter o f  the sample was about  ^ nun. The X -ray  tube was provided with a co}>per target and a nickel filter was used to  (ml o f f  the Kft wavelengths. T w o cylindri- (jal cameras were used and the radii o f  the cameras were measured accurately by taking the Dc^hye-Scherrer pattern o f  rocksalt. For the high tem perature cam era, the distance from  the film to the specimen is 2.84 erns and for the low tem pera­ture and room  tem perature camera, it is 5.25 cms. Several photographs under the same (?onrlitions were taken for each speedmen to test the genuineness o f  the results. Spacings were calculated from  the diam eters o f  the Debye-Seherrer rings which were measured correct to about O.I mm.K E S V L T S A N D  D I 8 C H 8 S I O NThe spacings deduced from the Debye-8cherrer patterns due to the crystal at different temperatures m entioned above are given in Table I in which the spacings calculated from  the data o f  Mathieson, R obertson  and Sinclair (1950) are also included in the first colum n for com parison. The intensities o f  the ring are recorded as very strong (vs), strong (s), medium (m ), weak (w) and very weak (vw ). Some o f  the representative photographs o f  the D ebye-Scherrer pa t­terns obtained under different conditions are reproduced in Plate X IV .It can be seen from  Table I that the spacings observed for the crystal at room  tem perature (32®C) agree fairly well with the spacings calculated from  the data given by  Mathieson, R obertson  and S in cla ir ,(1950). The assignment o f  indices to  the planes was made b y  taking the structure factors o f  different planesT A B L E  ISpacingw o f  crystals o f  anthraceiu 'Cl'ystal Structure of Anthracene at Different Temperatureii f>39From the data o f Matiueflon, Hobertson & Sinclair (1950)I^ rosoni Investigati'iiPlaiif’H Sf>af inu'- at 32"(^ at 55"C at Hirerooltnl to 1 80* ( ’ mul hmught hack at 180 to 32001 » . 128 !». 120w *9.083 vw 9.120 w101 8.318100 7.04!010 6.030102 5.520o n 5.034111 4.885 4.888 w I.88SVW *1 977 vw *4.807 \ u 1.S88 w1 10 4.581 4.577 \s 1.577 vs *4.000 vs *4.557 vs 1.577 W002 4.504101 4.478201 4.170 4.184 s 4. 1 84 .s * 1.244 « *4. 144 s 1 184 s202 4. 159112 4.070103 3.051012 3 .6 t l111 3.500200 3.520 3.525 s 3 525 s 3.584 s 3.490 s 3.525 s203 3.483211 3.430 3.440 s 3.140 s 3.194 s 3.419 H :i.440 s1041023.349 3.1070032103.043 3.040 3.042 s 3 012 s *3.0!> 1 s *3.018 s 3.012 s020 3.0181130212.868 2.800 2 .80(i w 2 S0(i vw *2.925 vw *2.848 vw 2 .8t9» w121 2.8302011202.794 2.774 2.777 w 2 777 vw *2.825 vw ♦2.759 vw 2.777 w204 2.703112 2.761013 2.717301 2.072211 2.535022 2.517121 2.50322l3112.446 2.443 2.4 14 2.444 in 2 482 m2 428 w 2.444 m114 2.433103 2.348300 2.3472200042.2912.282 2.280 w 2 280 vw *2 333 vw2 208 w 2.280 w202 2.239205 2.217113 2.189310 2.187122 2.165014 2.134212 2.092105 2.0786 i 0 Q. 8 . R . Krishna M urtiT A B L E  I  (Contd,)From the data of Mathieflon, Robertson & Sinclair (1950)Planes Spacinprs. at 32‘^ CPresent Investigationat 55°C «t 80°CCooled to -1 8 0 '‘Cand -brought back at — l«0°O to 32°C22] 2.050 2.052 mw 2.052 mw 2.080 vw 2.035 w224 2.038 (brofld)30] 2.015030 2.012321 2.001 2.004 vw 1.987 vw 2.004 vw031 1.964 1.968 vw 1.968 vwI3f 1.956130 1.934 1.930 vw 1.922 vw 1.930 vw311 1.912104 1,879411 1.853 1.855 m 1. S55 in 1.884 m 1.840 m 1.855 m320 1.852203 1.841131 1.835♦ These spacings arc used to calculate dimensions of the unit cell.T A B L E  IIPlanesSfjacings in A.U. at — ]80®CSpacings in A.U. at 80^CCalculated from unit celldimensionsobserv<^Calculated from unit celldimensionsobserved200 3.493 3.493 3.584 3.584211 3.420 3.419 3.494 3.494311 2.428 2.428 2.482 2.482004 2.267 2.268221 2.035 2.035 2.09032i 1.988 1.987 2.070 2.080(broad)130 1.922 1.921411 1.841 1.840 1.885 1.884into consideration. It  can be seen from  T able I that the spacings at 32°C agree with those given by  M athieson, R obertson  and Sinclair (1950) and there­fore the dim ensions o f  unit cell are given as a =  8.561 A .U ., b == 6.036 A .U ., 0=11*163 A.U* and fi =  124° 42 ' as reported  b y  those authors.URl ^ N A M U R T IflATE XIV.(0 (a)m(b)(c‘)(d)(<^)Debye-Scherrcr patierus of anthracene(a) Specimen at 8o‘ C ( Radius of Camera : 2.8.( (jris )(b) Specimen at 55' C ( Radius of Camera : 2.84 nns )(c) Specimen at 32'^ C ( Radius of Camera : ;,.2r, cms)(d) Specimen at - iMo^ 'C ( Radius of Camera : ',.21 cms)(c) Specimen once cooled to - itio‘C and brought barkto 32‘ C ( Radius of Camera : f^ .25 cms).I t  is further ev id en t from  the Table I that all the spacings for the crystal m aintained at 180 C are consistently shorter than the corresponding spacings for the crysta l at 32°C  and when the crystal is brought back to  32°C, after it is once coo led  to  — 180°C, the spacings agree with those at room  temperature. Since new  D ebye-Scherrer rings do not appear in the pattern obtained for the crystal at — 180°C, it can  be concluded that the unit cell only contracts at — 180°C and no appreciable distortion takes |>lace. The dimensions t)f the unit cell calcu lated  from  the spacings o f  the p l^ e s  (001), (111), (110), (120), (210) and (021) for the crystal at — 180°C are giV^n below.Crystal Structure of Anthracene at Different Temperatures 541a =  8.647 A .U . c =  11.090 A .U . andb =  6.000 A .U . /i =  1 2 f  10'.Taking the dim ensions o f  the unit cell l|)r the crystal at room temperature as those reported  b y  M athieson etal (1960) ihe mean coefficients o f  expansions, OLa, oci, and in the directions along the t h r ^  crystallographic axes in the range 32®C to  — 180°C can be calculated. The calculated values are=  7 7 .5 x l0 - « , af, =  27.62 x l 0 “ » ^  31.06 X  10 '«.T he dim ensions o f  the unit cell for the crystal a t— 196®C reported by  K ozhin and K ita iG ordsk ii (1953) agree fairly well with those obtained in the present investigation  excepting the value o f  a. B ut since they reported values for the dim ensions o f  the unit cell at 20°C lower than those reported by  Mathieson etal (1950) the mean values o f  coefficients o f  expansion do not agree with those obtained from  the data reported  by  them.I t  can be seen from  Table I  that the spacings for ihe crystal at 80® C are com paratively  higher than those obtained for the crystal at 32®C. B ut as no new rings appear in the Debye-Scherrer pattern nor does the pattern change even slightly  when the crystal is heated to  80®C, it can be concluded that only therm al expansion o f  the unit cell takes place with the rise o f  tem perature to 80°C. The dim ensions o f  the unit cell in the crystal at 80®C calculated from spacings o f  (111), (110), (120), (004), (021) and (201) are found to  bea =  8.696 A .U . c =  11.310 A .U . andb =  6.160 A .U . P =  124® 28'.T he m ean values o f  coefficients o f  expansion a* and in the range from  32®C to  80®C are obtained asa« =  32.86 X 10“ ®, =  39.36 x  10~® and == 27.46 x  lO^*.I t  can  be seen that the mean values o f  coefficients o f  expansion in the high tem perature range are about ten tim es higher than those in the low  tem perature region.542 G. S. B. Krishna MwtiIt can be seen from Table I that the values ctf spacings in the crystal at 5 5 T  are almost the same as those for the crystal at 32^C. This might be due to the reason that in this temperature range the coefficient o f  expansion is small so that appreciable change in the spacings does not tdke place. The spacings, however, increase abruptly when the temperature is raised above 55°C and the coefficient o f expansion increases enormously. The values o f  the spacings o f  other planes calculated from the dimensions o f  the unit cell for the crystal at low and high temperatures are given in Table II  together with those obseived. It can be seen that these two sets o f values agree fairly well with each other.The low frequency Raman lines o f  anthracene at different temperatures have not been investigated thoroughly and it would be interesting to find out whether these lines undergo abrupt changes with the change in the temperature o f  the crystal from 32'"C to 80^C, because in the case o f  jo-dichlorobenzene such a change has been observed by previous authors.A C K N O W L E D G M E N TThe author wishes to express his indebtedness to Professor S. C. Sirkar, D .bc., F.N .I. for his kind help and invaluable guidance throughout the progress o f  this w'ork.H  E  F E  R  E  N  E  SBanerjoc, K., 1930, Ind. J. Phyn,, 4, 557.Bragt', Sir William, 1923, Proc. Phys, f^ oc. Land, 8S. 167.Krishna Murti. 0 . S. R., and Sen. 8. N., 19.5fi. Iml. J. Phyn., 30. 242.Kozhin, V. M., and KitaiGorodskii, A. T., 19.53, Zhur. fiz. Khim., 27, No. 11, 1276. Mathieson, A. M., Kolxjrtaon. ,J. M.. and Sinelnir, V. 0.. 10.50, Acln. rry/it., 8. 245. Robertson. .1. M., 1933, Z. Knst., 84, 321.1933, Proc. Hoy. fior. Lorirl., 5.140, 79,

The Crystal Structure of Anthracene at Different Temperatures

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/1990/1/The%20crystal%20structure%20of%20anthracene_G%20S%20R%20Krishna%20Murti.pdf

The Crystal Structure of Anthracene at Different Temperatures

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