Creator:
Date Created:1958
Place Created:
Keywords:polymorphism at high pressure
Context:article from scientific journal
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1958
Tom' 120, Mi 5
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(npedcmaeAeHO amdeMUKOM H. B. EeAoeuM 22 III 1958)
rioJiHMopcj)Hoe npebpamehhe uepHH aBjiaeTCH eAHHCTBeHHHM b HacTonmee BpeMH H3BecTHbiM (})a30BbiM npeBpaiueHneM nepBoro poAa, npH kotopom nponc-xoaht pe3Koe yMeHbineHHe nocToflHHoft KpHcrajuiimecKOH pemeTKH, a cHMMeTpHH peilieTKH He H3MeH5ieTCH.
nojiHMop(J)Hoe npeBpameHHe uepHH npn CBepxBHCOKHx AaBjieHHnx 6hjio BnepBbie o6Hapy>KeHo Bphajkmchom (1). JlaycoH h IOaH (2) npoBejin peHTreHoB-CKoe HCCJiefloBaHHe M0AHt}>HKau.HH uepHH, oSpasyromeficH npn bmcokom flaBJie-hhh. eiopomkobbih o6pa3eu noMemajiCH b SepHjuiHeByio 6ou6y h noABeprajicn jiabjiehhio b 15 000 kF-cm-2. EipH stom aabjiehhh c Hero chhmajiacb AeSae-rpaMMa. OKa3ajiocb, hto uepHH npH 15 000 kF-cm-2, TaK jke KaK h npn aTMo-c(j)epHOM AaBJieHHH, HMeeT KySniecKyio rpaHeneHTpnpoBaHHyio pemeTKy. FIo-CTOHHHbie peilieTKH nph aabjiehhhx 1 h 15 000 KF-CM"2 paBHbl, COOTBeTCTBeHHO, 5,14 h 4,84 a. 06iu.ee h3mehehheofitema npn ok3thh uephh ao 15 000 kF-cm"2 ■cocTaBJiaeT 16,6%. JlaycoH h IOaH npeAnoJioJKHJiH, hto ripoTeKarorn.ee npn Bbico-khx aaBjieHHHx npeBpameHHe HAeHTHHHO npeBpameHHio, o^HapyjKeHHOMy He-cKOJibKo paHee Tpom6om h Ookcom (3) npn aTMOc^epHOM AaBJieHHH h hh3khx TeMnepaTypax, h hto sto npebpamehhe cbh3ah0 c nepexoAOM sjieKTpoHa H3 4/-coctohhhh b 5 d-COCTOHHHe. IllyX h CrypAHBaHT (4) HCCJie^OBajIH KpHCTajUIH-^ecKyio CTpyKTypy uepHH npH hh3khx TeMnepaTypax. Hmh dbiJio n0Ka3aH0, hto npn TeMnepaType —179° o6pa3eu nepnH npeACTaBJineT co6oh CMecb BHCOKOTeM-nepaTypHoft h HH3KoTeMnepaTypHofl moan<})hkau,hh (6yneM ofiosha^atb hx b AaJibHenmeM a-Ce h a'-Ce). 06e MOAH<})HKai],hh HMeiOT KySnqecKyio rpaHeueHTpH-poBaHHyro pemeTKy. Ooctohhhbie pemeTKH: a-Ce a = 5,14 A, a'-Ce a = =4,82 A. OdteMHuft 3cfxf>eKT cocTaB^neT 16,5% ot a-moah(}>HKaii,HH.
JlnxTep, PhShhhh h BepemarHH (5) HCCjieAOBajra qacTb P — T-AHarpaMMbi uepHH b HHTepBajie TeMnepaTyp ot —71 ao +94,5°. OnpeAeJieHHe aabjiehhh a —> a'-npeBpam,eHHH np0H3B0AHJi0Cb no CKanKy OKHMaeMOCTH. ri0Ka3aH0, hto AaBjieHHe a —>- a'-npeBpameHHH uepHH noBbiinaeTCfl c yBejinneHHeM TeMnepaTypbi, a 06-beMHbiH 3(}x|)eKT npn yBe/iHieHHH TeMnepaTypbi npeBpameHHH 33MeTHo yMeHbmaeTca. BejiHHHHa oSteMHoro scfj^KTa npn komh3thoh TeMnepaType oneheha b 8%.
CoxpaHeHHe chmmctphh pemeTKH h yMeHbineHHe pa3HocTH yAejibHbix ofi-be-mob a- h a'-(f)a3 BAOJib KpHBofl n03B0JiaeT npeAnoJioJKHTb cymecraoBaHHe KpHTH-lecKOH tohkh Ha KpHBofl nojiHMop(})Horo npeBpameHHH uepHH. /I.JIH npOBepKH 9Toro npeAnoJioKeHHH npoBeAeHo AaJibHeftmee HccjieAOBaHne P — T-AHarpaMMbi UepHH c noMomtio MeTOAHKH TepMorpacfttmecKoro aHajiH3a (6), n03B0JiHi0meH npoBOAHTb HccjieAOBaHne (j)a30Bbix npeBpameHHH BemecTBa npH AaBJieHnnx ao 35000kF -cm-2 h TeMnepaTypax ao >650°. hccjieaobahne np0B0AH^0Cb Ha uepHH, coAepJKameM (b %) < 0,75 Nd, <0,75 Pr, 0,01 Fe, <M0-4 Pb. rHApocTa-
THiecKoe AaBjieHHe co3AaBajiocb KOMnpHMHpoBaHHeM eMecH H3oneHTaHa c HOp-MaJibHbiM nehtahom b MyjibTHWiHKaTope CBepxBbicoKoro aabjiehhh. zlabjiehhe H3MepHJIOCb MaHraHHHOBbIM MaHOMeTpOM C TOHHOCTbK) + 100 kF'CM-2, TeMne-paTypa — TepMonapofl me;ie3o — hhxpom c towhoctbio ± 1,5°.
1021
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no AaHHbiM TepMorpaMM nocipoeHa KpHBan KOJiHMecTBO a'-c|>a3bi — AaB-jieHHe npn TeMnepaType 20° (cm. pnc. 3). npeBpameHHe a a' HanHHaeTCH npH aabjiehhh, 6jih3kom 7000 kF-cm"2, h kohnaetch npn 10000 kF-cm-2. TepBajie AaB^eHHH 7700—8350 kF-cm-2 o6pa3yeTCH 70% a'-Ce. KoHen, npeBpameHHH HBjineTCH 6ojiee pa3MbiTbiM. YBejiKqeHHe Bbi-AepwKH nocjie KajKAoro noBbiine-hhh AaBJieHHH (BnjIOTb AO HeCKOJlb-
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Kan bhaho h3 pHC. 1, c noBbimeHHeM AaBjieHHH TeMnepaTypa paBHOBecHH a- h a'-Ce noBbiinaeTCH no jiHHefiHOMy 3aKOHy. FaHreHC yrjia HaKJiotfa npHMofl paBHOBecHH a — a' k och aabjiehhh paBeH 0,0225 rpaA/kf-cm-2. baojib kphboh paBHOBecHH c yBeJiHMeHHeM AaBjieHHH nponcxoAHT yMeHbnieHHe BeJiHHHHbi Ten-^oBoro, a cjieAOBaTe^bho, h o6i>eMHoro 3(}xJ)eKTa npebpamehhh. nocTOhhctbo yrjia HaKJioHa kphboh paBHOBecHH k och aabjiehhh cbhaetejibctbyet o tom, mto TenJioBoft h o6T>eMHbiH 94x})eKTHi yMeHbmaioTCH no oSineMy 3aKOHy.
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nojiaran, hto TenjioBoft h oSteMHbift sc}xj)eKTbi npeBpameHHH nepHH npn nOBblHieHHH AaBJieHHH AeHCTBHTeJIbHO CTpeMHTCH K HyJIIO, MOJKHO CAeJiaTb CJie-AyiomHe npeAnojio)KeHHH o aajibhehmem xoAe KpHBofl paBHOBecHH a-Ce h a'-Ce:
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2.	KpHBan (J)a30Boro npeBpameHHH nepBoro poAa KOHuaeTCH b KpHTH^ecKOH TOHKe. Bbime kphthmeckofl toikh het hh (})a30Boro npeBpameHHH nepBoro, hh. (})a3oBoro npeBpameHHH BToporo poAa.
nocrynn.no 10 III 1958
UHTHPOBAHHAH JIHTEPATyPA
1 P. W.Bridgman, Proc. Am. Acad. Arts and Sci., 62, 207 (1927). 2 A. W. L a w-. son, Ting Yuan Tang, Phys. Rev., 76, 301 (1949). 3 F. T r o m b e, M. F o e x, Ann. Chim., 19, 416 (1944). 4 A. F. S c h u c h, J. H. Sturdivant, J. Chem. Phys., 18, 145 (1950). 5 A. H. J1 h x t e p, 10. H. P a 6 h h h h, JI. B e p e m a r h h, )K3T®, 33,610 (1957). 6 B. n. B y t y 3 o b, C. C. B o k in a, M. T. T o h h k 6 e p r, flAH, 108, Ms 5 (1956). 7 P. W. Bridgman, Proc. Am. Acad. Arts and Sci., 79, 164 (1951). 8 P. W. Bridgman, Proc. Am. Acad. Arts and Sci., 81, 213 (1952).
1023.