Menene Olivine Crystal Structure? {0} Polinovel

Tsarin crystal na Olivine ya ƙunshi tsari na orthorhombic inda keɓaɓɓen silicon{0} oxygen tetrahedra (SiO₄) ke haɗe ta hanyar cations na ƙarfe da ke mamaye wuraren octahedral. Ana iya ganin wannan tsarin a matsayin makusanci hexagonal na kusa{2}}cushe na atom ɗin oxygen, tare da rabin ɓangarorin octahedral cike da magnesium ko ions baƙin ƙarfe da ɗaya - na takwas na ɓoyayyiyar tetrahedral da silicon ke mamaye.

Ƙungiyar olivine tana yin kristal a cikin tsarin kristal orthorhombic a ƙarƙashin rukunin sararin samaniya Pbnm (wanda kuma aka sanya shi azaman Pnma a madadin saitunan). Wannan ma'auni na asali yana bayyana yadda atom ɗin ke tsara kansu a cikin lattice ɗin kristal kuma kai tsaye yana rinjayar abubuwan ma'adinai na zahiri.

Tantanin tantanin halitta ya ƙunshi nau'ikan ƙira guda huɗu (Z{0}}) kuma yana baje kolin gatura guda uku waɗanda basu daidaita ba waɗanda ke tsaka-tsaki a kusurwoyi daidai. Don forsterite (Mg₂SiO₄), sigogin lattice na yau da kullun suna kusan=4.75 Å, b=10.20 Å, da c=5.98 Å. A cikin fayalite (Fe₂SiO₄), waɗannan sigogi suna faɗaɗa kaɗan zuwa=4.82 Å, b=10.48 Å, da c=6.09 Å saboda babban radius ionic na baƙin ƙarfe idan aka kwatanta da magnesium.

Ƙungiyar sararin samaniya ta Pbnm tana bayyana mahimman bayanai na tsarin. Wannan rukunin sararin samaniya ya ƙunshi jirage masu saukar ungulu na madubi da cibiyar jujjuyawa, ƙirƙirar ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ma'aunin atomiki. Matsayin oxygen daban-daban na crystallographically guda uku (O1, O2, O3) sun kasance a cikin tsarin, tare da O1 da O2 suna kwance akan jiragen madubi yayin da O3 ke da matsayi na gaba ɗaya ba tare da kwatance na musamman ba.

A tsakiyar tsarin olivine ya ta'allaka ne da keɓaɓɓen SiO₄⁴⁻ tetrahedron, inda atom ɗin siliki na tsakiya ya haɗu da haɗin gwiwa tare da atom ɗin oxygen guda huɗu. Waɗannan tetrahedra sun kasance masu zaman kansu gaba ɗaya - ba sa raba atom ɗin oxygen tare da tetrahedra maƙwabta, suna rarraba olivine azaman nesosilicate ko orthosilicate. Kowane Si{3}}O bond yana auna kusan 1.63-1.66 Å kuma yana nuna ƙarfin haɗin kai.

Madaidaicin tetrahedra a cikin fuskantarwa, yana nuni sama da ƙasa tare da layuka masu layi ɗaya da crystallographic c{0}} axis. Wannan tsari na musanya yana haifar da tashoshi a cikin tsarin inda cations na ƙarfe zasu iya zama. Ion silicon yana ɗaukar rukunin yanar gizo na musamman na crystallographically wanda ke zaune akan jirgin madubi, ma'ana duk atom ɗin silicon da ke cikin tsarin suna da alaƙa da ayyukan ƙima.

Ƙarfe cations (musamman Mg²⁺ ko Fe²⁺) sun mamaye rukunin rukunin octahedral guda biyu masu lakabi M1 da M2. Wurin M1 yana zaune akan cibiyar jujjuyawar kuma ya samar da wata karkatacciyar octahedron tare da ƙwayoyin oxygen guda shida kewaye. Ƙarfe{4}} Tsawon haɗin oxygen a cikin M1 kewayo daga kusan 2.07{9}}2.13 Å don magnesium. Shafin M2 yana kwance akan jirgin madubi kuma yana haifar da girma, mafi girma octahedron na yau da kullun tare da nisan MO wanda ya kai 2.04-2.21 Å.

Bambanci tsakanin shafukan M1 da M2 yana da tasiri mai mahimmanci ga yadda ƙungiyoyi daban-daban ke rarraba kansu a cikin tsarin. A cikin jerin mafita na baƙin ƙarfe{{3}magnesium, Mg²⁺ da Fe²⁺ suna nuna ɗan zaɓin rukunin yanar gizo{4}}dukansu sun mamaye rukunin M1 da M2 ba tare da zaɓi mai ƙarfi ba. Koyaya, a cikin calcium - yana ɗauke da zaitun kamar monticellite (CaMgSiO₄), ions Ca²⁺ mafi girma sun fi dacewa su shiga mafi faffadan rukunin M2 yayin da Mg²⁺ yana fifita ƙaramin matsayi na M1.

olivine crystal structure

Wata hanyar da za a iya kwatanta tsarin olivine yana jaddada sublatice na oxygen. Oxygen anions suna samar da tsararru kusan hexagonal kusa-cushe (hcp) da aka jera tare da axis-. Wannan tsarin yana ba da ɓangarorin da silicon da cations na ƙarfe suka sanya kansu.

A cikin wannan tsari na hcp oxygen, cations na ƙarfe sun cika rabin ɓangarorin octahedral da ake da su, yayin da atom ɗin silicon sun mamaye kashi ɗaya - na takwas na ɓoyayyen tetrahedral. Wannan zaɓaɓɓen wurin zama yana haifar da sifa na olivine stoichiometry na M₂SiO₄, inda M ke wakiltar nau'ikan ƙarfe na ƙarfe.

Kowane zarra na oxygen yana haɗe zuwa siliki ɗaya da atom ɗin ƙarfe uku, suna ƙirƙirar tsari mai girma uku{0}. Atom ɗin oxygen ɗin ba daidai suke ba- madaidaitan iskar oxygen guda uku (O1, O2, O3) suna da ɗan bambanci daban-daban mahallin haɗin gwiwa da nisa zuwa maƙwabtan maƙwabta. Wannan bambance-bambance a cikin rukunin oxygen yana ba da gudummawa ga haɓakar tsarin gabaɗaya kuma yana shafar kaddarorin kamar haɓakar thermal da matsawa.

Rarraba octahedra -wasu octahedra sun miqe a layi daya zuwa jirgin (100), haye -wanda ke da alaƙa da keɓaɓɓen SiO₄ tetrahedra. Wannan siffa mai ɗorewa ta zama mahimmanci musamman a ƙarƙashin matsin lamba, saboda yana haifar da yuwuwar zamewar jirage waɗanda ke yin tasiri ga injin olivine da abubuwan girgizar ƙasa a cikin rigar duniya.

Tsarin lu'ulu'u na Olivine yana ɗaukar ingantaccen bayani mai ci gaba tsakanin ƙarshen magnesium{0}}memba forsterite (Mg₂SiO₄) da ƙarshen baƙin ƙarfe{1}}member fayalite (Fe₂SiO₄). Wannan cikakkiyar kuskuren ya wanzu saboda Mg²⁺ (radius ionic ~ 0.72 Å) da Fe²⁺ (radius ionic ~ 0.77 Å) sun bambanta da girman kusan 7% kawai, yana ba su damar musanya kyauta ba tare da karkatar da tsarin crystal ba.

Abubuwan da aka haɗe ana bayyana su azaman kashi na molar, kamar Fo₇₀Fa₃₀ (ko kawai Fo₇₀), yana nuna 70% forsterite da 30% fayalite. Olivines na dabi'a daga duwatsun mafic yawanci suna fitowa daga Fo₅₀ zuwa Fo₉₀, yayin da zaitun mantle gabaɗaya sun fi magnisia, tare da abubuwan da ke kewaye da Fo₈₈ zuwa Fo₉₂.

Siffofin lattice suna haɓaka kusan layi tare da abun cikin ƙarfe. Kamar yadda Fe²⁺ ya maye gurbin Mg²⁺, tantanin halitta yana faɗaɗa saboda girman baƙin ƙarfe yana matsar da atom ɗin gaba kaɗan. Wannan dangantakar tana da iya tsinkaya har za a iya amfani da girman tantanin halitta don tantance abun da ke ciki na olivine tare da madaidaicin daidaito.

Bayan babban Mg{0}Fe canji, tsarin olivine na iya haɗa ƙananan adadin sauran cations. Calcium yana shiga tsarin a cikin ƙididdiga masu yawa, yana fifita rukunin M2. Manganese (a cikin tephroite, Mn₂ SiO₄) na iya maye gurbin magnesium ko baƙin ƙarfe gaba ɗaya. Matsakaicin adadin nickel, chromium, har ma da ƙarfe na ƙarfe (Fe³⁺) na iya musanya zuwa rukunin gidajen octahedral, kodayake a cikin ƙananan rabbai.

Tsarin Olivine ya kasance barga ne kawai a ƙarƙashin takamaiman matsa lamba da yanayin zafi. Yayin da zurfin ya karu a cikin Duniya, tsarin olivine ya zama mara amfani da kuzari kuma yana canzawa zuwa polymorphs masu yawa tare da sifofi daban-daban na crystal.

A kusan zurfin kilomita 410 (daidai da matsi a kusa da 14 GPa), olivine yana jure wa canjin yanayi na zamani zuwa wadsleyite. Wannan sauyi ya ƙunshi gagarumin sake fasalin tsarin inda iskar oxygen ke motsawa daga kusa da hexagonal kusa-har zuwa wani tsari mai siffar cubic. Wadsleyite yana riƙe da ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun tsarin kashin baya{5}kamar tsari tare da wasu ƙwayoyin siliki a cikin daidaitawar octahedral.

Zurfafa a cikin rigar Duniya, a zurfin zurfin kilomita 520 (18-20 GPa), wadsleyite yana canzawa zuwa ringwoodite, wanda ke ɗaukar tsarin kashin baya mai siffar kubik. A cikin ringwoodite, duk silicon sun mamaye wuraren octahedral maimakon matsayi na tetrahedral. Waɗannan sauye-sauyen lokaci suna haifar da ɗimbin yawa ba zato ba tsammani wanda masana kimiyyar ƙasa suka gano a matsayin katsewa a cikin saurin girgizar ƙasa.

Matsalolin da waɗannan sauye-sauye ke faruwa ya dogara da yanayin zafi da abun da ke ciki. Iron{1} arziƙin olivine yana canzawa a ƙananan matsi fiye da nau'ikan wadatar magnesium{2}. A digiri 800 , tsarkakakken forsterite yana canzawa zuwa wadsleyite a 11.8 GPa, yayin da waɗsleyite -zuwa{7}} miƙa mulki na ringwoodite yana faruwa sama da 14 GPa. Ƙarshen ƙarfe -memba fayalite ya tsallake tsarin wadsleyite gaba ɗaya kuma yana canzawa kai tsaye zuwa ahrensite (baƙin ƙarfe{11}}analogin ringwoodite) a ƙananan matsi.

olivine crystal structure

Tsarin olivine yana mayar da martani ta hanyar anisotropy zuwa matsa lamba{0}} daban-daban na kwatance crystallographic damfara a farashi daban-daban. M2 octahedron yana matsawa cikin sauri fiye da M1 octahedron a duk abubuwan da aka tsara daga forsterite zuwa fayalite. Wannan bambance-bambancen matsawa yana faruwa ne saboda rukunin M2 yana da ƙarar farko mafi girma da ƙarin sassauci a cikin tsarin haɗin gwiwa.

Single{0}crystal X- binciken diffraction na ray har zuwa 8 GPa ya bayyana cewa M2{7}} Tsawon haɗin gwiwa yana gajarta da sauri fiye da haɗin M1-O a ƙarƙashin matsin lamba. M1 octahedron ya zama ɗan ƙaramin ƙarfi tare da haɓaka abun ciki na baƙin ƙarfe, wanda a zahiri yana haifar da dumbin modules (juriya ga matsawa gabaɗaya) don ƙara ɗanɗano kaɗan daga forsterite zuwa fayalite-sakamakon farko na rashin fahimta tunda ƙarfe ya fi magnesium nauyi.

Zazzabi yana rinjayar tsarin daban. Dumama yana sa naúrar tantanin halitta ta faɗaɗa, tare da b{1}}axis yana nuna mafi girman haɓakar haɓakar thermal. Nazarin yanayin zafi mai girma{3} akan forsterite har zuwa digiri 900 ya nuna cewa M{5}} Tsawon haɗin gwiwa yana ƙaruwa da tsari, amma ainihin tsarin topology yana kasancewa baya canzawa har sai yanayin narkewa ya kusanci.

SiO₄ tetrahedra yana da ƙarfi sosai idan aka kwatanta da ƙarfe{0}oxygen octahedra. Si- Tsawon haɗin kai yana canzawa kaɗan tare da ko dai matsa lamba ko zafin jiki saboda ƙaƙƙarfan halayen haɗin Si-O. Yawancin sassauƙan tsari yana zuwa daga gyare-gyare a cikin M-O Tsawon haɗin gwiwa da kusurwoyi tsakanin polyhedra maimakon matsawa na polyhedra da kansu.

Tsarin tsarin olivine yana samo mahimman aikace-aikacen fasaha a cikilithium iron phosphate batura(LiFePO₄ ko LFP). An gano shi azaman kayan cathode a cikin 1996, lithium iron phosphate yana ɗaukar nau'in tsarin tsarin olivine iri ɗaya kamar ma'adinan ma'adinai, kodayake tare da ƙungiyoyin phosphate suna maye gurbin keɓaɓɓen silicate tetrahedra.

A cikin LiFePO₄, tsarin yana kiyaye ma'anar orthorhombic (ƙungiyar sararin samaniya Pnma/Pbnm) tare da sigogin lattice a=6.008 Å, b=10.334 Å, da c=4.693 Å. Ƙarfin zarra sun mamaye wuraren octahedral (wanda ke samar da FeO₆ octahedra), yayin da atom ɗin phosphorus ke zaune a wuraren tetrahedral (masu samar da PO₄ tetrahedra), kwatankwacin yadda ƙarfe da siliki ke shirya a cikin olivine na ma'adinai.

Bambancin maɓalli yana cikin ƙarin cations na lithium. Lithium ions suna zaune a cikin tashoshi octahedral a cikin tsarin, wanda aka shirya cikin tsarin zigzag. A yayin cajin baturi da fitarwa, ions lithium za a iya jujjuya su da su kuma a saka su cikin waɗannan tashoshi ba tare da ruguza ainihin tsarin olivine ba. Iron ɗin yana yin hawan keke tsakanin Fe²⁺ da Fe³⁺ don kiyaye ma'auni yayin da lithium ke motsawa da fita.

Wannan kwanciyar hankali na tsari{0}}wanda aka gada daga ingantacciyar gine-ginen olivine{1}} yana ba batirin LiFePO₄ halaye na musamman na aminci da tsawon rayuwa. Ƙarfin P{3}O haɗin gwiwar haɗin gwiwa a cikin tetrahedra phosphate suna tsayayya da sakin iskar oxygen, yana hana yanayin zafi da ke addabar wasu sinadarai na lithium{4}} ion. Batirin LFP na kasuwanci na iya cimma fiye da caji 3,000 - zagayawa yayin da suke riƙe ƙarfi.

Tsarin olivine yana ba da iyakancewa ɗaya: ions lithium dole ne su yaɗu ta hanyar tashoshi ɗaya{0} tare da gatura mai ƙima maimakon motsawa cikin yardar kaina cikin girma uku. Wannan yana ƙuntata ƙarfin ƙarfin ionic da ƙarfin ƙimar. Masu bincike suna magance wannan ta hanyar nanostructuring (rage girman barbashi don gajarta hanyoyin yaduwa) da kuma murfin carbon (ingantaccen aikin lantarki). Abubuwan da aka gyara kamar lithium manganese iron phosphate (LMFP) suna kula da tsarin zaitun yayin da ake maye gurbin manganese don wani ƙarfe don ƙara ƙarfin aiki.

Fahimtar tsarin olivine na zamani ya zo da farko daga dabarun rarrabuwar ra'ayi na X{{0}. William Lawrence Bragg da GB Brown sun fara ƙaddamar da tsarin kristal na forsterite a cikin 1926 ta amfani da hanyoyin X{5} na farko. Ayyukan su sun kafa olivine kamar yadda ya ƙunshi keɓaɓɓen SiO₄ tetrahedra{7}}asashen fahimta don silicate mineralogy.

Single -crystal X- bambance-bambancen ray ya kasance ma'aunin gwal don ƙayyadaddun ƙayyadaddun tsari. Karamin kiristocin olivine (yawanci 0.1{4}}0.5 mm) ana hawa akan goniometer kuma ana jujjuya shi ta katakon X-ray. Sakamakon rarrabuwar kawuna ya ƙunshi dubunnan tunani guda ɗaya, kowanne yana wakiltar saitin jirage daban-daban na crystallographic. Sophisticated software yana sake sabunta matsayi na atomic, ma'aunin zafi da zafi, da wuraren zama don dacewa da ingantattun rarrabuwar kawuna.

Neutron diffraction yana ba da ƙarin bayani, musamman mahimmanci don gano ƙwayoyin hydrogen (a cikin matakan hydrous) da bambanta tsakanin abubuwa masu irin wannan ƙididdiga na lantarki kamar magnesium da aluminum. Gwaje-gwajen Neutron na buƙatar manyan lu'ulu'u da wurare na musamman tare da tushen neutron, amma suna ba da daidaito mafi girma don tantance sifofin maganadisu da wasu wurare masu haske.

Microscope na lantarki mai watsawa (TEM) yana nazarin tsarin olivine a nanoscale, yana bayyana lahani, iyakokin yanki, da bambance-bambancen gida waɗanda ba a ganuwa ga hanyoyin rarrabawa. Babban ƙudurin TEM yana iya ɗaukar ginshiƙan ginshiƙan atomic, kai tsaye yana hango tsarin atom ɗin. Wannan ya zama mai ƙarfi musamman lokacin nazarin samfuran nakasassu ko sauye-sauyen lokaci inda tsarin ya bambanta ta ƙananan nisa.

Raman da infrared spectroscopy binciken tsarin olivine ta hanyar yanayin girgiza. SiO₄ tetrahedron yana da mahimman hanyoyin girgiza guda huɗu, kuma mitocin su sun dogara da Si{1}} Ƙarfin haɗin gwiwa da mahalli na kewaye. Haɗin kai yana rinjayar waɗannan mitoci masu girgiza ta hanyoyin da za a iya tsinkaya-forsterite yana nuna kololuwa daban-daban fiye da fayalite saboda Fe-O bond sun fi Mg-O bond. Waɗannan fasahohin bakan gizo suna aiki marasa lalacewa kuma suna iya siffanta ƙananan samfuran ko haɗawa.

Tsarin crystallographic kai tsaye yana sarrafa abubuwan gani na olivine. Ma'adinan yawanci yana bayyana zaitun - kore saboda Fe²⁺ ions a cikin daidaitawar octahedral suna ɗaukar haske a cikin takamaiman tsayin raƙuman ruwa, yana watsa kore. Tsaftataccen forsterite ba shi da launi zuwa koɗaɗɗen rawaya -kore, yayin da ƙarfe{4}}arfafan abubuwan da ke fitowa sun fito duhu kore zuwa launin ruwan kasa-baƙi.

Olivine yana nuna karaya ga juna maimakon tsagewa saboda tsarin tsarin keɓewar tetrahedra guda uku - yana haifar da haɗin gwiwa mai ƙarfi daidai a kowane bangare. Babu wani jirgin sama na rauni a cikin tsarin da ya yi daidai da tsarin zane a cikin micas ko Layer silicates. Lokacin da olivine ya karye, yana karyewa ba bisa ka'ida ba a cikin tsarin maimakon tsagawa tare da takamaiman jirage na crystallographic.

Ƙimar ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun anisotropic {{0}halayen jiki sun bambanta tare da jagorar crystallographic. Gudun motsin girgizar ƙasa ya bambanta dangane da yanayin yaduwa dangane da gatari. Hanyar saurin sauri ya yi daidai da axis -, matsakaiciyar gudu zuwa ga axis, da jinkirin gudu zuwa ga axis. Wannan anisotropy seismic a cikin mantle olivine yana taimaka wa masana kimiyyar lissafi su fassara shugabanci da girman kwararar rigar.

Taurin (6.5{3}}7 akan sikelin Mohs) da yawa (3.27-3.37g/cm³ na forsterite, 4.39 g/cm³ na fayalite) duka suna da alaƙa da matsatsin tsarin tsari da ƙarfin haɗin ƙarfe-oxygen. Tsarin iskar oxygen mai yawa da gajeriyar nisan ƙarfe-oxygen a cikin tsarin olivine suna haifar da ma'adinai mai ƙarfi, mai juriya ga yanayin sinadarai a ƙarƙashin zurfin yanayin duniya.

olivine crystal structure

Lu'ulu'u na olivine na gaske suna ƙunshe da ƙarancin tsari waɗanda ke tasiri sosai ga halayensu. Lalacewar maki sun haɗa da guraben aiki (abubuwan zarra masu ɓacewa), tsaka-tsaki (ƙarin atom ɗin da aka matse zuwa wuraren da ba a saba da su ba), da lahani na musanya (abubuwan da ba daidai ba a wuraren al'ada). Waɗannan lahani, ko da yake ba kasafai ba, suna sarrafa ƙimar yaɗuwa da ƙarancin wutar lantarki ta hanyar ƙirƙirar hanyoyin motsi na ionic.

Rarrabuwa{0}}lalacewar layi inda tsarin tsarin crystallographic na yau da kullun ya rushe{1}} yana mamaye kaddarorin injin olivine. Ragewa (motsin waɗannan lahani na layi ta hanyar crystal) yana wakiltar babbar hanyar nakasa a cikin mantle olivine a ƙarƙashin ma'auni na yanayin ƙasa. Ƙayyadaddun tsarin zamewa (jirgin sama na crystallographic da kwatance na motsi) sun ƙayyade yadda hatsin olivine ke lalacewa da haɓaka abubuwan da aka fi so.

Ƙarfafa lahani kamar iyakokin hatsi da iyakoki tagwaye suna haifar da musaya inda tsarin kristal ke canzawa daga wannan yanayin zuwa wani. Waɗannan iyakoki suna shafar ƙarfin injina kuma suna ba da hanyoyin yaduwa cikin sauri don canjin sinadarai. Iyakokin subgrain -ƙananan-Iyakokin kusurwa waɗanda suka haɗa da tsararru na ɓarna{4}} suna haɓaka cikin naƙasasshiyar olivine kuma suna rikodin tarihin naƙasa.

A saman duniya, yanayin olivine yana sauri duk da tsarinsa mai ƙarfi. Kwayoyin ruwa na iya shiga tare da lahani da iyakokin hatsi, suna amsawa tare da tsarin olivine. Samfuran da aka fi sani da shi shine serpentine, wanda aka kafa lokacin da kwayoyin ruwa suka shiga cikin tsarin: 2Mg₂SiO₄ + 3H₂O → Mg₃Si₂O₅(OH)₄ + Mg(OH)₂. Wannan halayen yana faɗaɗa ƙarar asali ta 30-40% kuma yana lalata tsarin tushen olivine, maye gurbin shi da yadudduka silicate.

Sauran samfuran gyare-gyare sun haɗa da iddingsite (kyakkyawan - cakuda hatsi na ƙarfe oxides da ma'adinan yumbu) da bowlingite (ƙarfe mai hydrated -mai ɗaukar silicates). Waɗannan hanyoyin sauye-sauye suna tafiya cikin sauri tare da fashe da gefuna na crystal inda ruwa zai iya samun damar tsarin cikin sauƙi. Cikakken maye gurbin pseudomorphic zai iya faruwa, inda kayan da aka canza yana riƙe da siffar crystal na waje yayin da tsarin ciki ya juyo gaba ɗaya zuwa ma'adanai na biyu.

Menene ya sa tsarin olivine ya bambanta da sauran ma'adanai na silicate?

Olivine ya ƙunshi keɓaɓɓen SiO₄ tetrahedra waɗanda ba sa raba kwayoyin oxygen tare da juna, suna bayyana shi azaman nesosilicate. Wannan ya bambanta da silicates sarkar (kamar pyroxenes), silicates na takarda (kamar micas), da silicates na tsarin (kamar ma'adini) inda tetrahedra ke raba oxygens don samar da tsararren tsari. Keɓaɓɓen tetrahedra ya ƙirƙira babbar hanyar sadarwa mai girma guda uku - wacce ke riƙe tare da haɗin ƙarfe{3}} iskar oxygen.

Me yasa olivine yana da rukunin karfe biyu daban-daban (M1 da M2)?

Siffar ma'auni na orthorhombic da ƙayyadaddun tsarin tattarawa na atom ɗin oxygen suna haifar da wurare biyu na crystallographically daban-daban na octahedral masu girma dabam dabam da murdiya. M1 yana zaune akan cibiyar juyawa kuma yana ƙarami kuma ya fi karkacewa, yayin da M2 ke kwance akan jirgin madubi kuma ya fi girma kuma ya fi na yau da kullun. Wannan bambance-bambancen yana rinjayar waɗanne cations sun fi son waɗanne rukunin yanar gizon kuma suna sarrafa kayan zahirin kayan.

Ta yaya abun da ke ciki ke shafar tsarin crystal olivine?

Kamar yadda ƙarfe ke maye gurbin magnesium a cikin jerin fayalite{0}, rukunin tantanin halitta yana faɗaɗa iri ɗaya saboda Fe²⁺ ya fi Mg²⁺ girma. Asalin tsarin topology ya kasance baya canzawa{2}} rukunin sararin samaniya, matsayi iri ɗaya, mahallin daidaitawa iri ɗaya. Tsawon haɗin gwiwa yana ƙaruwa kaɗan, amma tsarin atom ɗin ya kasance daidai da kamanni. Wannan yana ba da damar cikakken bayani mai ƙarfi tsakanin mambobi na ƙarshe{5}.

Shin tsarin olivine zai iya ɗaukar ruwa ko wasu marasa ƙarfi?

Daidaitaccen tsarin olivine ba ya ƙunshi ƙungiyoyin hydroxyl ko ruwan kwayoyin halitta. Koyaya, adadin hydrogen na iya haɗawa azaman lahani{1}yawanci azaman ƙungiyoyin OH waɗanda ke musanya da atom ɗin oxygen ko zama a cikin wuraren da ba kowa. Waɗannan abubuwan da ke cikin "ruwa" sun ragu sosai (yawanci<50 ppm by weight), but even trace hydrogen significantly affects electrical conductivity and diffusion rates. Water content increases with pressure, making transition zone olivine polymorphs potentially important water reservoirs in Earth's deep interior.

Tsarin crystal na olivine yana nuna halaye masu zuwa:

Tsarin Crystal: Orthorhombic tare da rukunin sararin samaniya Pbnm (ko Pnma a madadin saitin)

Lattice Parameters:

Forsterite: a ≈ 4.75 Å, b ≈ 10.20 Å, c ≈ 5.98 Å

Fayalite: a ≈ 4.82 Å, b ≈ 10.48 Å, c ≈ 6.09 Å

Tubalan Ginin: SiO₄ tetrahedra keɓe wanda aka haɗa ta ƙarfe{0}}oxygen octahedra (MO₆)

Rukunin Ƙarfe: Shafukan octahedral guda biyu daban-daban (M1 da M2) masu girma dabam da murdiya

Matsayin Oxygen: Wuraren oxygen daban-daban na crystallographically guda uku a cikin sashin asymmetric

Nau'in Tsari: Hexagonal na kusa{0}}cushewar iskar oxygen tare da cations a cikin ɓangarorin tetrahedral da octahedral

Rabewa: Nesosilicate (orthosilicate) saboda keɓaɓɓen raka'a tetrahedral

Haɗin kai: Si a cikin 4-coordination (tetrahedral), M cations a cikin 6-coordination (octahedral)

Wannan tsarin tsarin yana tabbatar da ƙarfi sosai, yana riƙe da kwanciyar hankali a cikin jeri daban-daban a cikin mahallin yanayin ƙasa yayin da kuma yana ba da tushe ga kayan batir na ci gaba a aikace-aikacen fasaha. Haɗin tsarin olivine na ƙaƙƙarfan covalent Si{{1} O bond tare da sassauƙan ƙarfe{2}} daidaitawar iskar oxygen ya sa ya zama ɗaya daga cikin mafi mahimmancin tsarin ma'adinai na Duniya.