Kowa ya san cewa ruwa yana faruwa a cikin jihohi uku na haɗuwa. Mun sanya kettle a kan, kuma ruwan ya fara tafasa da ƙafewa, yana juya daga ruwa zuwa gaseous. Mun sanya shi a cikin injin daskarewa, kuma ya fara juya zuwa kankara, ta haka yana motsawa daga ruwa zuwa wani wuri mai mahimmanci. Koyaya, a ƙarƙashin wasu yanayi, tururin ruwa da ke cikin iska na iya shiga cikin lokaci mai ƙarfi nan da nan, yana ƙetare lokacin ruwa. Mun san wannan tsari ta sakamakonsa - kyawawan alamu akan tagogi a ranar sanyi mai sanyi. Masu sha'awar mota, a lokacin da suke zazzage ruwan ƙanƙara daga gilashin iska, galibi suna bayyana wannan tsari ta amfani da ba kimiyya sosai ba, amma mai raɗaɗi da haske. Wata hanya ko wata, an rufe cikakkun bayanai game da samuwar kankara mai girma biyu a cikin sirri tsawon shekaru da yawa. Kuma a kwanan nan, a karon farko, ƙungiyar masana kimiyya ta duniya ta sami damar hango tsarin atomic na ƙanƙara mai girma biyu a lokacin da aka samu. Wane sirri ne ke ɓoye a cikin wannan tsari na zahiri mai sauƙi, ta yaya masana kimiyya suka yi nasarar gano su, kuma ta yaya bincikensu ke da amfani? Rahoton ƙungiyar bincike zai gaya mana game da wannan. Tafi
Tushen bincike
Idan muka yi karin gishiri, to kusan dukkanin abubuwan da ke kewaye da mu suna da girma uku. Duk da haka, idan muka yi la'akari da wasu daga cikinsu da kyau, za mu iya samun masu girma biyu. Ƙanƙarar ƙanƙara da ke tasowa a saman wani abu shine babban misali na wannan. Kasancewar irin wadannan tsare-tsare ba boyayye ba ne ga al'ummar kimiyya, domin an yi nazari akai akai. Amma matsalar ita ce, yana da wuya a iya hango abubuwan da za su iya daidaitawa ko tsaka-tsakin da ke cikin samuwar kankara 2D. Wannan shi ne saboda matsalolin banal - rashin ƙarfi da raunin tsarin da ake nazarin.
Abin farin ciki, hanyoyin bincike na zamani suna ba da damar yin nazarin samfurori tare da ƙananan tasiri, wanda ke ba da damar samun iyakar bayanai a cikin ɗan gajeren lokaci, saboda dalilai na sama. A cikin wannan binciken, masanan kimiyya sun yi amfani da microscopy ba tare da lamba ba, tare da ƙarshen allurar microscope mai rufi da carbon monoxide (CO). Haɗin waɗannan kayan aikin dubawa yana ba da damar samun hotuna na ainihin-lokaci na tsarin gefen ƙanƙara mai girman girman bilayer hexagonal mai girma biyu da aka girma akan saman zinari (Au).
Microscope ya nuna cewa yayin samar da ƙanƙara mai girma biyu, nau'ikan gefuna guda biyu (ɓangarorin da ke haɗa kifaye biyu na polygon) a lokaci guda suna kasancewa tare a cikin tsarinsa: zigzag (zigzag) da siffar kujera (kujera).
Arm kujera (hagu) da zigzag (dama) gefuna ta amfani da graphene a matsayin misali.
A wannan mataki, samfuran sun daskare da sauri, suna ba da damar yin nazarin tsarin atomic daki-daki. An kuma gudanar da yin samfuri, wanda sakamakonsa ya yi daidai da sakamakon lura.
An gano cewa a cikin yanayin samuwar haƙarƙari na zigzag, an ƙara ƙarin ƙwayar ruwa zuwa gefen da ake ciki, kuma dukkanin tsari yana daidaitawa ta hanyar haɗin gwiwa. Amma game da samuwar hakarkarin kujeru, ba a sami ƙarin wasu ƙwayoyin cuta ba, waɗanda ke da bambanci da ra'ayoyin gargajiya game da haɓakar ƙanƙara mai lamba biyu mai lamba biyu da abubuwa masu girma dabam dabam.
Me yasa masana kimiyya suka zaɓi microscope wanda ba ya tuntuɓar ikon atomatik don duban su maimakon na'urar duba microscope (STM) ko microscope na lantarki (TEM)? Kamar yadda muka riga muka sani, zaɓin yana da alaƙa da wahalar nazarin tsarin ɗan gajeren lokaci da ƙarancin ƙanƙara mai nau'i biyu. A baya an yi amfani da STM don yin nazarin kankara na 2D da aka girma a sama daban-daban, amma irin wannan nau'in na'urar microscope ba ta kula da matsayin tsakiya, kuma titinsa na iya haifar da kurakuran hoto. TEM, akasin haka, yana nuna daidaitaccen tsarin atomic na hakarkarin. Duk da haka, samun hotuna masu inganci na buƙatar electrons masu ƙarfi, waɗanda za su iya canzawa cikin sauƙi ko ma lalata tsarin gefuna na kayan XNUMXD masu haɗin gwiwa, ban da madaidaicin gefuna a cikin kankara XNUMXD.
Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwararren Ƙwaƙwalwa na Ƙaƙwalwa na Ƙaƙwalwa na Ƙaƙwalwa na Ƙaƙwalwa ) ba shi da shi, kuma wani tip mai rufaffiyar CO yana ba da damar nazarin ruwa mai tsaka-tsaki tare da ƙananan tasiri akan kwayoyin ruwa.
Sakamakon bincike
Hoto #1
An shuka ƙanƙara mai girma biyu a saman Au(111) a zafin jiki na kusan 120 K, kuma kauri ya kai 2.5 Å (1).
Hotunan STM na kankara (1c) da madaidaicin hoton Fourier mai sauri (saka a cikin 1) nuna tsari mai kyau mai lamba hexagonal tare da lokaci-lokaci na Au(111)-√3 x √3-30°. Kodayake cibiyar sadarwar H-haɗin kankara ta 2D tana iya gani a cikin hoton STM, cikakken yanayin tsarin gefen yana da wuya a tantance. A lokaci guda, AFM tare da sauyawar mitar (Δf) na yanki guda ɗaya ya ba da hotuna mafi kyau (1d), wanda ya sa ya yiwu a hango sassan tsarin da ke da siffar kujera da zigzag. Jimillar tsayin bambance-bambancen biyu yana kamanta, amma matsakaicin tsayin haƙarƙarin magabata ya ɗan fi tsayi (1b). Haƙarƙari na zigzag na iya girma har zuwa 60 Å tsayi, amma masu siffar kujera sun zama an rufe su da lahani a lokacin da aka samu, wanda ya rage tsayin su zuwa 10-30 Å.
Bayan haka, an gudanar da hoton AFM na tsari a tsayin allura daban-daban (2).
Hoto #2
A mafi girman tsayin tsayi, lokacin da siginar AFM ya mamaye mafi girman odar lantarki, saiti biyu na √3 x 3 sublatices a cikin bilayer kankara mai girma biyu an gano, ɗayan wanda aka nuna a ciki. 2 (hagu).
A ƙananan tsayin allura, abubuwa masu haske na wannan yanki suna fara nuna alkibla, ɗayan kuma ya juya zuwa wani nau'i mai siffar V.2a, a tsakiya).
A mafi ƙarancin tsayin allura, AFM yana bayyana tsarin saƙar zuma tare da bayyanannun layukan da ke haɗa sublatices biyu, mai tunawa da H-bonds (2a, zuwa dama).
Ƙididdigar ka'idar aiki mai yawa ya nuna cewa ƙanƙara mai girma biyu da ke girma a saman Au(111) ya yi daidai da tsarin kankara mai Layer biyu masu haɗaka (2s), wanda ya ƙunshi yadudduka na ruwa hexagonal biyu lebur. Hexagons na zanen gado biyu suna haɗuwa, kuma kusurwar tsakanin kwayoyin ruwa a cikin jirgin yana da 120 °.
A cikin kowane Layer na ruwa, rabin kwayoyin ruwa suna kwance a kwance (daidai da ma'auni) yayin da sauran rabi suna kwance a tsaye (a tsaye zuwa ƙasa), tare da O-H ɗaya yana nunawa sama ko ƙasa. Ruwan kwance a tsaye a cikin Layer ɗaya yana ba da gudummawar H-bond zuwa ruwa a kwance a wani Layer, yana haifar da cikakken tsari mai siffar H.
AFM simulation ta amfani da quadrupole (dz 2) tip (2b) bisa ga samfurin da ke sama yana cikin kyakkyawar yarjejeniya tare da sakamakon gwaji (2a). Abin baƙin ciki, irin wannan tsayin daka na ruwa a kwance da na tsaye yana sa gano su da wahala yayin hoton STM. Koyaya, lokacin amfani da microscopy na ƙarfin atomic, ƙwayoyin nau'ikan nau'ikan ruwa biyu ana iya bambanta su a fili (2a и 2b dama) saboda mafi girman tsari na ƙarfin lantarki yana da matukar damuwa ga daidaitawar kwayoyin ruwa.
Hakanan yana yiwuwa a ƙara ƙayyade hanyar OH na ruwa a kwance da tsaye ta hanyar hulɗar tsakanin manyan sojojin lantarki da Pauli masu tsaurin ra'ayi, kamar yadda aka nuna ta layin ja. 2 и 2b (tsakiyar).
Hoto #3
A cikin hotuna 3 и 3b (Mataki na 1) yana nuna manyan hotunan AFM na zigzag da fis ɗin kujera, bi da bi. An gano cewa gefen zigzag yana girma yayin da yake kiyaye tsarinsa na asali, kuma tare da haɓakar gefen kujera mai siffar kujera, an sake dawo da gefen a cikin tsarin lokaci-lokaci na zobe 5756, watau. lokacin da tsarin haƙarƙarin lokaci-lokaci yana maimaita jerin pentagon - heptagon - pentagon - hexagon.
Ƙididdigar ka'idar aiki mai yawa ya nuna cewa fin zigzag da ba a sake ginawa ba da fin kujera 5756 sune mafi kwanciyar hankali. An kafa gefen 5756 ne sakamakon haɗe-haɗen tasirin da ke rage adadin haɗin haɗin hydrogen da ba a cika ba kuma yana rage ƙarfin kuzari.
Masana kimiyya sun tuna cewa jiragen saman ƙanƙara na ƙanƙara mai hexagonal yawanci suna ƙarewa a cikin haƙarƙarin zigzag, kuma haƙarƙari masu kama da kujera ba sa nan saboda yawan abubuwan haɗin hydrogen da ba su cika ba. Duk da haka, a cikin ƙananan tsarin ko kuma inda sarari ya iyakance, kujerun kujeru na iya rage ƙarfin su ta hanyar sake fasalin da ya dace.
Kamar yadda aka ambata a baya, lokacin da aka dakatar da haɓakar ƙanƙara a 120 K, an kwantar da samfurin nan da nan zuwa 5 K don ƙoƙarin daskare sifofin metastable ko canjin canji da kuma tabbatar da tsawon rayuwar samfurin don cikakken nazarin ta amfani da STM da AFM. Hakanan yana yiwuwa a sake gina tsarin haɓakar ƙanƙara mai girma biyu (hoto A'a. 3) godiya ga tip ɗin microscope mai aiki na CO, wanda ya sa ya yiwu a gano sifofin metastable da canji.
Game da haƙarƙari na zigzag, ana samun ɗaiɗaikun pentagons wani lokaci a haɗe zuwa madaidaicin hakarkarin. Za su iya yin layi a jere, suna yin tsararru tare da lokaci-lokaci na 2 x ruwa (ruwa shine madaidaicin ƙanƙara mai girma biyu). Wannan lura na iya nuna cewa ci gaban zigzag gefuna ya fara ne ta hanyar samuwar lokaci-lokaci tsararrun pentagons (3, Mataki na 1-3), wanda ya ƙunshi ƙara nau'i-nau'i na ruwa don pentagon (jajayen kiban).
Na gaba, an haɗa tsararrun pentagons don samar da tsari kamar 56665 (3, mataki na 4), sannan kuma ya dawo da ainihin bayyanar zigzag ta ƙara ƙarin tururin ruwa.
Tare da gefuna masu siffar kujera halin da ake ciki shine akasin haka - babu tsararru na pentagons, amma a maimakon haka ana lura da gajerun gibba kamar 5656 a gefen. Tsawon fin 5656 ya fi guntu fiye da na 5756. Wannan yana yiwuwa saboda 5656 fin yana da matukar damuwa kuma ba shi da kwanciyar hankali fiye da 5756. Farawa tare da fin kujera 5756, zoben 575 suna canzawa a cikin gida zuwa zoben 656 ta ƙara biyu. tururin ruwa (3b, mataki na 2). Na gaba, zoben 656 suna girma a cikin madaidaiciyar hanya, suna samar da gefen nau'in 5656 (3b, mataki na 3), amma tare da iyakacin tsayi saboda tarin makamashi na lalata.
Idan an ƙara nau'i biyu na ruwa zuwa hexagon na fin 5656, nakasar na iya raguwa kaɗan, kuma wannan zai sake haifar da samuwar fin 5756 (3b, mataki na 4).
Sakamakon da ke sama yana da ma'ana sosai, amma an yanke shawarar tallafa musu da ƙarin bayanan da aka samu daga ƙididdige ƙididdige ƙimar tururin ruwa a saman Au (111).
An gano cewa XNUMXD tsibiran kankara mai nau'i biyu sun samu nasara kuma ba tare da tsangwama a saman ba, wanda ya yi daidai da binciken mu na gwaji.
Hoto #4
Akan hoton 4 Ana nuna tsarin haɗin gwiwa na gadoji akan hakarkarin zigzag mataki-mataki.
A ƙasa akwai kayan watsa labarai akan wannan binciken tare da kwatance.
Kayayyakin watsa labarai Na 1
Yana da kyau a lura cewa pentagon guda ɗaya da aka haɗe zuwa gefen zigzag ba zai iya aiki azaman cibiyar tsakiya na gida don haɓaka girma ba.
Kayayyakin watsa labarai Na 2
Maimakon haka, cibiyar sadarwa na pentagons na lokaci-lokaci amma ba tare da haɗin gwiwa ba ta fara farawa a gefen zigzag, kuma ƙwayoyin ruwa masu shigowa gaba ɗaya suna ƙoƙarin haɗa waɗannan pentagons, wanda ya haifar da tsarin tsarin sarkar nau'in 565. Abin baƙin ciki, ba a lura da irin wannan tsari ba a lokacin. lura a aikace, wanda ke bayyana gajeriyar rayuwar sa.
Kayayyakin watsa labarai na 3 da na 4
Ƙarin nau'in ruwa guda ɗaya yana haɗa nau'in nau'in nau'in 565 da pentagon da ke kusa, wanda ya haifar da samuwar tsarin nau'in 5666.
Tsarin nau'in nau'in 5666 yana girma a gefe don samar da nau'in nau'in nau'in 56665 kuma a ƙarshe ya haɓaka zuwa cikakkiyar haɗin gwiwa mai tsayi hexagonal.
Kayayyakin watsa labarai na 5 da na 6
Akan hoton 4b Ana nuna girma a yanayin haƙarƙari na kujera. Juyawa daga nau'in zoben 575 zuwa nau'in zoben 656 yana farawa daga Layer na ƙasa, yana samar da tsarin 575/656 mai hade wanda ba za a iya bambanta da nau'in fin 5756 ba a cikin gwaje-gwajen, tun da kawai saman Layer na kankara mai Layer biyu ne kawai za a iya kwatanta. yayin gwaje-gwajen.
Kayayyakin watsa labarai Na 7
Sakamakon gada 656 ya zama cibiyar nucleation don haɓakar haƙarƙarin 5656.
Kayayyakin watsa labarai Na 8
Haɗa kwayoyin ruwa guda ɗaya zuwa gefen 5656 yana haifar da ingantaccen tsarin ƙwayoyin cuta mara ɗabi'a.
Kayayyakin watsa labarai Na 9
Biyu daga cikin waɗannan ƙwayoyin ruwa da ba a haɗa su ba za su iya haɗawa daga baya zuwa ingantaccen tsarin heptagonal, suna kammala jujjuyawar daga 5656 zuwa 5756.
Don ƙarin cikakken sani tare da nuances na binciken, Ina ba da shawarar dubawa .
Epilogue
Babban ƙarshen wannan binciken shine cewa halayen da aka lura na sifofi yayin girma na iya zama gama gari ga kowane nau'in kankara mai girma biyu. Bilayer hexagonal ƙanƙara yana samuwa akan nau'o'in hydrophobic daban-daban da kuma ƙarƙashin yanayin tsarewar hydrophobic, sabili da haka ana iya la'akari da shi azaman kristal 2D daban (2D Ice I), samuwar wanda ba shi da hankali ga tsarin da ke cikin ƙasa.
Masana kimiyya sun ce har yanzu fasahar daukar hoto ba ta dace da yin aiki da kankara mai girma uku ba, amma sakamakon nazarin kankara mai nau'i biyu na iya zama tushen bayanin tsarin samuwar danginsa na volumetric. Ma'ana, fahimtar yadda sifofi masu girma biyu suka kasance muhimmin tushe don nazarin masu girma uku. Don haka ne masu binciken suka yi shirin inganta hanyoyin su a nan gaba.
Na gode da karantawa, ku kasance da sha'awar kuma kuyi kyakkyawan mako. 🙂
Wasu tallace-tallace 🙂
Na gode da kasancewa tare da mu. Kuna son labaran mu? Kuna son ganin ƙarin abun ciki mai ban sha'awa? Goyon bayan mu ta hanyar ba da oda ko ba da shawara ga abokai, , analog na musamman na sabar matakin shigarwa, wanda mu muka ƙirƙira muku: (akwai tare da RAID1 da RAID10, har zuwa 24 cores kuma har zuwa 40GB DDR4).
Dell R730xd 2x mai rahusa a cibiyar bayanan Equinix Tier IV a Amsterdam? Nan kawai a cikin Netherlands! Dell R420 - 2x E5-2430 2.2Ghz 6C 128GB DDR3 2x960GB SSD 1Gbps 100TB - daga $99! Karanta game da
source: www.habr.com