• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    A First-Principles Study on the Vibrational and Electronic Properties of Zr-C MXenes?

    2018-05-14 01:05:22ChangYingWang王昌英YongLiangGuo郭永亮YuanYuanZhao趙媛媛GuangLiZeng曾廣禮WeiZhang張偉CuiLanRen任翠蘭HanHan韓晗andPingHuai懷平
    Communications in Theoretical Physics 2018年3期
    關(guān)鍵詞:張偉

    Chang-Ying Wang(王昌英),Yong-Liang Guo(郭永亮),Yuan-Yuan Zhao(趙媛媛), Guang-Li Zeng(曾廣禮),Wei Zhang(張偉),Cui-Lan Ren(任翠蘭),Han Han(韓晗), and Ping Huai(懷平)

    1Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China

    2Department of Electronics and Communication Engineering,Henan Institute of Technology,Xinxiang 453003,China

    3Department of Physics,School of Physics and Optoelectronic Engineering,Nanjing University of Information Science and Technology,Nanjing 210044,China

    1 Introduction

    Recently,a great achievement has been made in the synthesization of new Zr-C materials.[1]The new produced Zr3C2Tz(T=F,O,OH)is composed by the Zr3C2block and the functionalized group.It belongs to a new class of two-dimensional(2D)materials,MXene(Mn+1XnTx),which is a type of 2D transitional metal carbide,nitride and carbonitride and can be prepared from layered nanolaminates by selective etching method.[1?2]The terminal groups T in MXene are usually oxygen(O),hydroxyl(OH)or fl uorine(F).The currently researching hotspot of material science,MAX phase,is one kind of layered nanolaminates.[3?5]Taking Zr-C MXene as an example,its precursors can be Zrn+1AlCn(n=1,2)(MAX phase),(n=2,3)layered nanolaminates.[6]

    In the past decades,more and more 2D materials are being investigated and synthesized for their excellent electronic properties,mechanical properties,optical properties and so on.[7?9]As the new discovered 2D materials,MXenes are currently expected to have numerous potential applications such as electronic devices[10?12]and electrode of Li ion batteries.[13?14]As the relatively early produced MXenes,2D Ti-C and Mo-C materials have been explored by many works within the framework of density functional theory(DFT).However the knowledge about Zr-C MXenes is scarce due to the late preparation of 2D Zr-based materials.Considering the fact that DFT has gained substantial achievements in material field,a firstprinciples investigations on the 2D ZrnCn?1(n=2,3,4)and their functionalized MXenes have been done in this work.[15?21]The geometry,phonon spectra,and electronic density of states(DOS)are explored to have a better understanding of the experimentally synthesized and theoretically potential Zr-C MXenes.

    The rest of this work is organized as follows.The computational methods are described in Sec.2.The discussions on the structural properties,vibrational properties,and electronic properties of ZrnCn?1(n=2,3 and 4)and their functionalized MXenes are given in Sec.3.The conclusion part is presented in Sec.4.

    2 Computational Methods

    All calculations in this work were performed with the VASP (Vienna Ab-initio Simulation Package)code[22]with projector-augmented plane wave(PAW)potentials[23]and Perdew-Burke-Ernzerhof (PBE)exchange-correlation functional.[24]The wave functions were expanded in a plane-wave basis set with an energy cuto ffof 500 eV.A Γ-centeredk-point sampling scheme over the Brillouin zone was used for all the calculations.2D bare and functionalized MXenes were investigated with the vacuum space being larger than 17?A to avoid any interaction of the MXene sheet with its periodically repeated images along thecaxis.A 18×18×2k-point mesh was used to optimize the structure of these 2D system.To check the dynamical stability of these 2D system,we calculated the phonon dispersion by using a supercell approach[25]as implemented in the PHONOPY code.[26]In these phonon calculations,a 4×4×1 supercell and 3×3×1k-point mesh were used.The symmetry nonequivalent Zr,Al and C atoms were displaced from their equilibrium positions by an amplitude of 0.02?A and the atomic forces induced by these small displacements were calculated within VASP.In the calculation of the DOS for pristine and chemical functionalized MXenes,a 42×42×3k-point mesh was used.

    3 Results and Discussions

    3.1 Structural Properties

    MXene can be prepared from layered nanolaminates by selective etching method.Theoretically there exist three types of Zr-C MXenes ZrnCn?1(n=2,3 and 4).They can be obtained from the Zr-Al-C nanolaminates(Zr2AlC(211),Zr3AlC2(312),Zr2Al3C4(234),Zr3Al3C5(335),Zr4Al3C6(436),Zr2Al4C5(245)and Zr3Al4C6(346)).The simulated Zr2C,Zr3C2and Zr4C3MXene structures as well as their possible precursors in Zr-Al-C system are depicted in Figs.1(a)–1(c).Generally,the pristine Zr-C MXenes are stabilized by the O,F,and OH functionalization during the etching process,thus generating nine kinds of functionalized MXenes.The top view of Zr2C is presented in Fig.1(d)and the possible adsorption sites(A,B and C)of functionalization atoms are also indicated in Fig.1(d).The chemical functionalization of the investigated MXenes have four possible con figurations:Con fi.1 has two functional groups adsorbed on the top of Zr atoms(site C),Con fi.2 has two functional groups located on the top of site B,Con fi.4 locates two functional groups on the top of site A and Con fi.3 is a combination of Con fi.2 and Con fi.4,in which one functional group locates on the top of site A and the other one on the top of site B.We compare the total energies of the four chemically adsorbed con figurations in Table 1 and find Con fi.2 has the lowest energy for all functionalized MXenes.This indicates that all functionalized species preferably adsorb on the top of site B.The side views of the most stable F,O,and OH functionalization structures of Zr2C are shown in Figs.1(e)–1(g),respectively.

    Fig.1 (Color online)Schematic illustrations of pristine and functionalized Zr-C MXenes.Side view of pristine Zr-C MXenes as well as their possible precursors in Zr-Al-C system:(a)Zr2C,(b)Zr3C2and(c)Zr4C3.(d)Top view of Zr2C.The large blue balls are the Zr atoms at the first layer and the small ones are those at the second layer.The symbol A represents the hollow site under which a carbon atom exists,B represents the hollow site under which there is no carbon atom,C is the top site of Zr atom.The rest three graphs are side views of(e)F,(f)O,and(g)OH functionalized Zr2C.The blue,red,black,purple,magenta and green balls indicate the Zr,Al,C,F,O and H atoms,respectively.

    The optimized lattice parameters of bare ZrnCn?1(n=2,3,4)and their corresponding F,O and OH functionalized MXenes are shown in Table 2.The lattice parameters of functionalized Zr2C are all elongated with respect to the bare Zr2C MXene.The OH-terminated ZrnCn?1(n=2,3,4)MXene has a larger lattice parameter than its F and O-terminated counterparts.The Zr3C2O2and Zr4C3O2have the smallest lattice parameter value among Zr3C2and Zr4C3series,respectively.The binding energy of the functionalized group in ZrnCn?1T2(n=2,3,4)(T=F,O,OH)is calculated according to the following equation:[27]

    where theandE(T)are the energies ofand the isolated functionalized group T,respectively.The binding energy can be used to predict the stabilities of the functionalizedMXenes.Our calculated binding energy of functionalizedMXenes are listed in Table 2.They are all large negative values,implying that the bareMXenes tend to be chemically decorated by the oxidizing group.On account of the computed binding energy,the stabilities of the functionalized Zr-C MXenes increase in the sequence of

    3.2 Vibrational Properties

    The stabilities of the bare and functionalized Zr-C MX-enes are explored by the calculation of their phonon spectra which are depicted in Fig.2.At the Γ point,the bare,and functionalized ZrnCn?1all have a quadratic fl exural acoustic phonon branch,similar to the other 2D materials,such as graphene,silicene,and phosphorene.[28?29]There exist no imaginary frequencies in all bare MXenes(Zr2C,Zr3C2and Zr4C3),indicating their dynamical stability.The imaginary frequency does not exist in the phonon dispersion of F,O,and OH functionalized Zr2C MXenes.The dynamical stability of these compounds indicates their possible existence,which is consistent with the previously reported results.[29]Moreover,the O-terminated Zr3C2and Zr4C3have no negative phonon modes,while the F and OH-terminated counterparts have small imaginary acoustic phonon branches around Γ point,which is consistent with the stabilities predicted from the binding energy of functionalized group.The imaginary frequency indicates the dynamical instability of F and OH-terminated Zr3C2and Zr4C3.However Zr3C2Tz(T=F,O,OH)MXenes have already been experimentally synthesized.[1]In consideration of the relatively small values of the calculated imaginary frequency,the unavoidable strain and temperature under experimental conditions might conquer the dynamical instability.

    Table 1 Total energies(eV)of con figurations 1-4 for F,O and OH functionalized Zr2C,Zr3C2,and Zr4C3 systems.The most stable functionalization structure is labeled in bold.

    Table 2 Optimized lattice parameters(?A)and calculated binding energy(eV)of functionalized group in bare ZrnCn?1(n=2,3,4),as well as the most stable F,O and OH functionalized con figuration.

    The phonon partial DOS of Zr-C MXenes are also calculated and depicted in Fig.2.In bare ZrnCn?1(n=2,3,4),the high-frequency phonon branches are contributed by the C atoms and the low-frequency ones come from the Zr atoms.In ZrnCn?1F2(n=2,3,4),the phonon dispersion spectra between 300 cm?1and 400 cm?1are mainly attributed to the vibration of the functionalized F atoms.In ZrnCn?1O2(n=2,3,4),the terminal O induced phonon vibrational frequencies are higher than the ones contributed by Zr atoms and lower than the ones caused by the C atoms.And the vibrational peak of the O atoms locates in the region of 400 cm?1and 450 cm?1.In ZrnCn?1(OH)2(n=2,3,4),the phonon branches above 3000 cm?1are the result of the vibrations of H atoms.In all calculated phonon partial DOS,the positions of the vibrational peaks have a close relationship with the atom species.In summary,the heavy atoms correspond to the low-frequency peaks,while the light atoms correspond to the high-frequency peaks.Except for the effect of the atomic mass,the interactions among atoms have also a signi ficant in fl uence on their vibrational frequencies.Take ZrnCn?1F2(n=2,3,4)as an example,the vibrational frequencies of F atoms are more close to the Zr atoms than the C atoms,even though its atomic mass is much closer to the C atoms.

    Fig.2(Color online)Phonon dispersion spectra and partial DOS of bare ZrnCn?1(n=2,3,4),as well as their most stable F,O,and OH functionalized con figuration.Zr represents the super ficial Zr layers,and Zr2 is the rest of the Zr layers.

    3.3 Electronic Properties

    The electronic properties of pristine and surface functionalized Zr-C MXenes have been calculated and presented in Fig.3–5.Pristine MXenes(Zr2C,Zr3C2,and Zr4C3)are all metallic with large DOS contributed by the Zr atom,especially the super ficial Zr layer,at the Fermi energy.The large Zr DOS peaks at the Fermi level might cause the instability of bare Zr-C MXenes,suggesting that the bare Zr-C MXenes tend to be functionalized by chemical groups.

    When ZrnCn?1(n=2,3,and 4)MXenes are functionalized by F,O,and OH,new hybridization states appear and the DOS of MXenes at the Fermi level are reduced.The adsorbed F group hybridizes with the Zr atom at about?7.5 eV in all kinds of Zr-C MXenes and obtains one electron from the pristine ZrnCn?1(n=2,3,and 4).

    The new hybridization state between hydrogen and oxygen atoms of the hydroxyl group locates around?9.5 eV in OH terminated Zr-C MXenes.Other additional bands in hydroxyl functionalized Zr-C MXenes are at about?6 eV and they are contributed by the interaction of the O atoms and the super ficial Zr atoms.The functionalized O atom gives rise to large DOS in ZrnCn?1O2(n=2,3,and 4)at about?4.4 eV and acquires two electrons from the pristine ZrnCn?1(n=2,3,and 4).The Fermi energy of the O terminated ZrnCn?1(n=2,3,and 4)MXenes shifts downward to the right edge of the hybridization state of C atom and Zr atom.In Zr2CO2,the Fermi level situates just at the band gap of the empty Ti band and the hybridized band of Zr,C and O.

    Fig.3(Color online)Total and localized DOS of pristine and surface functionalized Zr2C MXenes.The vertical line represents the Fermi level.

    Fig.4 (Color online)Total and localized DOS of pristine and surface functionalized Zr3C2MXenes.Zr1 represents the super ficial Zr layers,and Zr2 is the middle Zr layer.The vertical line represents the Fermi level.

    Fig.5 (Color online)Total and localized DOS of pristine and surface functionalized Zr4C3MXenes.Zr1 represents the super ficial Zr layers,and Zr2 is the rest of the Zr layers.The vertical line represents the Fermi level.

    In Zr3C2and Zr4C3,the super ficial Zr layers hybridize with the functionalized group in the low energy region,while the rest of the Zr atoms interact with the C atoms in the relatively high energy region.As thenvalue ofdecreases,the thicknesses of Zr slabs gradually decline,which lowers the DOS near the Fermi level.Especially for(ZrnCn?1)O2,Zr4C3O2is still a metal,Zr3C2O2is a semimetal,while Zr2CO2becomes a semiconductor with a band gap of 0.8 eV.

    4 Conclusions

    The fundamental properties of Zr-C MXenes are important to their potential applications.In this work,a systematic first-principles study on the structural,vibrational,and electronic properties of Zr-C MXenes have been conducted.The most stable con figurations for Zr-C MXene are the ones that the terminal groups F,O,and OH locate on the common hollow site of the super ficial Zr layer and its adjacent C layer.The stabilities of the functionalized Zr-C MXenes increase in the sequence ofaccording to the species of the terminal group.Among all the investigated MXenes,F and OH-terminated Zr3C2and Zr4C3have small imaginary acoustic phonon branches around Γ point while the others have no negative phonon modes.The pristine MXenes(Zr2C,Zr3C2and Zr4C3)are all metallic with large DOS contributed by the Zr atom at the Fermi energy.When functionalized by F,O and OH,new hybridization states appear and the DOS at the Fermi level are reduced.Especially for ZrnCn?1O2,Zr4C3O2is still a metal,Zr3C2O2is a semimetal,while Zr2CO2becomes a semiconductor.

    We also thank the Supercomputing Center of Chinese Academy of Sciences(SCCAS)and the Shanghai Supercomputing Center for Computer Resources.

    [1]J.Zhou,X.Zha,F.Y.Chen,et al.,Angew.Chem.Int.Ed.55(2016)5008.

    [2]M.Naguib,M.Kurtoglu,V.Presser,et al.,Adv.Mater.23(2011)4248.

    [3]Q.Huang,H.Han,R.Liu,et al.,Acta Mater.110(2016)1.

    [4]H.Han,D.Wickramaratne,Q.Huang,et al.,RSC Adv.6(2016)84262.

    [5]H.Wang,H.Han,G.Yin,et al.,Materials 10(2017)103.

    [6]C.Y.Wang,H.Han,Y.Y.Zhao,et al.,J.Am.Ceram.Soc.101(2018)756.

    [7]G.Fiori,F.Bonaccorso,G.Iannaccone,et al.,Nat.Nano.9(2014)768.

    [8]F.Xia,H.Wang,D.Xiao,et al.,Nat.Photon.8(2014)899.

    [9]D.Akinwande,N.Petrone,and J.Hone,Nat.Commun.5(2014)5678.

    [10]M.Khazaei,M.Arai,T.Sasaki,et al.,Adv.Funct.Mater.23(2013)2185.

    [11]A.N.Enyashin and A.L.Ivanovskii,J.Phys.Chem.C 117(2013)13637.

    [12]M.Khazaei,A.Ranjbar,M.Ghorbani-Asl,et al.,Phys.Rev.B 93(2016)205125.

    [13]J.Hu,B.Xu,C.Ouyang,et al.,RSC Adv.6(2016)27467.

    [14]M.Naguib,J.Halim,J.Lu,et al.,J.Am.Chem.Soc.135(2013)15966.

    [15]C.Y.Wang,H.Han,K.Shao,et al.,Chin.Phys.B 24(2015)097101.

    [16]R.Yang,B.Tang,T.Gao,and B.Y.Ao,Commun.Theor.Phys.66(2016)447.

    [17]Z.G.Wang,X.Y.Yang,S.J.Qin,and C.L.Wang,Commun.Theor.Phys.68(2017)125.

    [18]N.Erum and M.A.Iqbal,Commun.Theor.Phys.66(2016)571.

    [19]C.Y.Wang,H.Han,D.Wickramaratne,et al.,RSC Adv.7(2017)8421.

    [20]K.Shao,H.Han,W.Zhang,et al.,Comp.Mater.Sci.137(2017)186.

    [21]K.Shao,H.Han,W.Zhang,et al.,J.Nucl.Mater.490(2017)181.

    [22]G.Kresse and J.Furthmüller,Phys.Rev.B 54(1996)11169.

    [23]P.E.Bl?chl,Phys.Rev.B 50(1994)17953.

    [24]J.P.Perdew,K.Burke,and M.Ernzerhof,Phys.Rev.Lett.77(1996)3865.

    [25]K.Parlinski,Z.Q.Li,and Y.Kawazoe,Phys.Rev.Lett.78(1997)4063.

    [26]A.Togo,F.Oba,and I.Tanaka,Phys.Rev.B 78(2008)134106.

    [27]T.Hu,Z.Li,M.Hu,et al.,J.Phys.Chem.C 121(2017)19254.

    [28]G.Qin,Q.B.Yan,Z.Qin,et al.,Phys.Chem.Chem.Phys.17(2015)4854.

    [29]Y.Uˇgur,?.Ayberk,K.P.Nihan,et al.,Nanotechnology 27(2016)335702.

    猜你喜歡
    張偉
    Nonlinear vibration of iced cable under wind excitation using three-degree-of-freedom model?
    文化名家
    ——張偉
    昨天 今天
    金秋(2020年14期)2020-10-28 04:15:40
    Solvability for Fractional p-Laplacian Differential Equation with Integral Boundary Conditions at Resonance on Infinite Interval
    Relationship between characteristic lengths and effective Saffman length in colloidal monolayers near a water-oil interface?
    藝術(shù)百家:張偉 何是雯
    看得到的轉(zhuǎn)變
    中華家教(2018年9期)2018-10-19 09:30:00
    藝術(shù)廣角
    數(shù)學(xué)潛能知識月月賽
    真的記住了
    故事會(2014年10期)2014-05-14 15:24:18
    成人亚洲精品一区在线观看 | 人妻制服诱惑在线中文字幕| 九九在线视频观看精品| 日韩不卡一区二区三区视频在线| 69av精品久久久久久| 国产亚洲一区二区精品| kizo精华| av播播在线观看一区| 精品久久国产蜜桃| 午夜激情福利司机影院| 尾随美女入室| 只有这里有精品99| 乱人视频在线观看| 建设人人有责人人尽责人人享有的 | 亚洲乱码一区二区免费版| 国产亚洲91精品色在线| 人妻少妇偷人精品九色| 成人一区二区视频在线观看| 日韩人妻高清精品专区| 一级a做视频免费观看| 国产亚洲av嫩草精品影院| av线在线观看网站| 精品酒店卫生间| 91aial.com中文字幕在线观看| 亚州av有码| 国模一区二区三区四区视频| 国产一区有黄有色的免费视频 | 天美传媒精品一区二区| 亚洲av电影不卡..在线观看| 黄色日韩在线| 久久精品夜夜夜夜夜久久蜜豆| 久久精品久久精品一区二区三区| 中文字幕亚洲精品专区| h日本视频在线播放| 91狼人影院| 看十八女毛片水多多多| 美女国产视频在线观看| 亚洲aⅴ乱码一区二区在线播放| 成人鲁丝片一二三区免费| 在线播放无遮挡| 亚洲av中文av极速乱| 夫妻午夜视频| 天堂俺去俺来也www色官网 | 一级毛片电影观看| 成年人午夜在线观看视频 | 美女大奶头视频| 日本猛色少妇xxxxx猛交久久| 最近手机中文字幕大全| 青春草视频在线免费观看| 亚洲国产高清在线一区二区三| 精品一区二区免费观看| 午夜福利视频1000在线观看| 亚洲在线观看片| 美女脱内裤让男人舔精品视频| 热99在线观看视频| 性色avwww在线观看| 狠狠精品人妻久久久久久综合| 国产午夜精品一二区理论片| 两个人的视频大全免费| www.色视频.com| 在线观看免费高清a一片| 男插女下体视频免费在线播放| 五月天丁香电影| 亚洲精品第二区| 女人被狂操c到高潮| 欧美极品一区二区三区四区| 直男gayav资源| 黄色欧美视频在线观看| 80岁老熟妇乱子伦牲交| 特级一级黄色大片| 亚洲精品aⅴ在线观看| 色综合亚洲欧美另类图片| 嫩草影院入口| 日韩欧美国产在线观看| 国产精品一区二区性色av| 国产亚洲91精品色在线| 三级国产精品片| 国产成人午夜福利电影在线观看| 午夜福利在线在线| 一级毛片久久久久久久久女| 亚洲人成网站在线播| 白带黄色成豆腐渣| 亚州av有码| 成年人午夜在线观看视频 | 菩萨蛮人人尽说江南好唐韦庄| 在线观看免费高清a一片| 九九爱精品视频在线观看| 成年版毛片免费区| 日韩伦理黄色片| 免费观看无遮挡的男女| 亚洲av在线观看美女高潮| 三级男女做爰猛烈吃奶摸视频| 婷婷六月久久综合丁香| 国产精品嫩草影院av在线观看| 国产色婷婷99| 亚洲乱码一区二区免费版| 中国国产av一级| 国产亚洲一区二区精品| 精品不卡国产一区二区三区| 亚洲国产欧美在线一区| 麻豆乱淫一区二区| 大香蕉久久网| 在线免费观看的www视频| 免费观看的影片在线观看| 精品久久久久久久久久久久久| 一个人看的www免费观看视频| 美女国产视频在线观看| 在线 av 中文字幕| 午夜免费男女啪啪视频观看| av免费观看日本| 成人午夜高清在线视频| 亚洲av在线观看美女高潮| 欧美日韩综合久久久久久| 国产成人免费观看mmmm| 欧美xxxx性猛交bbbb| 日日摸夜夜添夜夜添av毛片| 久久精品国产自在天天线| 亚洲aⅴ乱码一区二区在线播放| 别揉我奶头 嗯啊视频| 国产高清不卡午夜福利| 久久久国产一区二区| 国产成人aa在线观看| 国产精品不卡视频一区二区| 看非洲黑人一级黄片| 一区二区三区免费毛片| 午夜免费观看性视频| 亚洲精品视频女| 18禁在线播放成人免费| 午夜久久久久精精品| 日本-黄色视频高清免费观看| 亚洲国产av新网站| 男女边吃奶边做爰视频| 亚洲成人中文字幕在线播放| 亚洲国产精品专区欧美| 国产av不卡久久| 性色avwww在线观看| 乱码一卡2卡4卡精品| 免费av不卡在线播放| 日韩精品有码人妻一区| 搡老妇女老女人老熟妇| 亚洲av免费高清在线观看| 高清毛片免费看| 中国美白少妇内射xxxbb| 成人亚洲欧美一区二区av| av在线观看视频网站免费| 3wmmmm亚洲av在线观看| 亚洲精品色激情综合| 啦啦啦中文免费视频观看日本| 在线免费观看不下载黄p国产| 免费人成在线观看视频色| 国产老妇女一区| 91av网一区二区| 国产 亚洲一区二区三区 | 精品久久久久久电影网| 久久久国产一区二区| 男女视频在线观看网站免费| 2021少妇久久久久久久久久久| 久久精品久久久久久久性| 中文字幕亚洲精品专区| 色5月婷婷丁香| 18禁动态无遮挡网站| 赤兔流量卡办理| 国产成人精品久久久久久| 国产伦精品一区二区三区视频9| 欧美性猛交╳xxx乱大交人| 亚洲国产色片| av在线老鸭窝| 国产男女超爽视频在线观看| 日韩欧美精品v在线| 青春草亚洲视频在线观看| 麻豆乱淫一区二区| 国产午夜福利久久久久久| 国产一区二区亚洲精品在线观看| 别揉我奶头 嗯啊视频| 我的老师免费观看完整版| av一本久久久久| 国产91av在线免费观看| av.在线天堂| 国产亚洲最大av| 欧美 日韩 精品 国产| 夫妻性生交免费视频一级片| 淫秽高清视频在线观看| 日本一本二区三区精品| 亚洲欧美精品专区久久| 在线 av 中文字幕| 国产精品.久久久| 亚洲av免费在线观看| 国产麻豆成人av免费视频| 天天一区二区日本电影三级| 久久精品综合一区二区三区| 精品人妻一区二区三区麻豆| 亚洲欧美日韩无卡精品| 丰满少妇做爰视频| 亚洲久久久久久中文字幕| 中文字幕av在线有码专区| 高清午夜精品一区二区三区| 国产不卡一卡二| 国产黄色小视频在线观看| 久久精品国产亚洲网站| 国产在线男女| 国产女主播在线喷水免费视频网站 | 搡老妇女老女人老熟妇| 99热这里只有是精品在线观看| 啦啦啦韩国在线观看视频| 亚洲国产高清在线一区二区三| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | 人妻系列 视频| 三级经典国产精品| 一级毛片电影观看| 99久久人妻综合| 欧美精品一区二区大全| 亚洲国产精品成人综合色| 欧美97在线视频| 97人妻精品一区二区三区麻豆| 禁无遮挡网站| 九草在线视频观看| or卡值多少钱| 欧美97在线视频| 国产不卡一卡二| 国产精品久久久久久精品电影小说 | 国产成人aa在线观看| 九草在线视频观看| 国产高清国产精品国产三级 | 欧美 日韩 精品 国产| 日本黄大片高清| 亚洲精品久久午夜乱码| 可以在线观看毛片的网站| 看非洲黑人一级黄片| 国产老妇伦熟女老妇高清| 免费看光身美女| 国产亚洲91精品色在线| 如何舔出高潮| 久久热精品热| 国产亚洲精品久久久com| 熟妇人妻久久中文字幕3abv| 淫秽高清视频在线观看| 伊人久久国产一区二区| eeuss影院久久| 简卡轻食公司| 国产免费福利视频在线观看| av卡一久久| 97超碰精品成人国产| 日韩制服骚丝袜av| 国产精品久久久久久久久免| 蜜臀久久99精品久久宅男| videossex国产| av在线亚洲专区| av免费在线看不卡| 午夜福利成人在线免费观看| av在线观看视频网站免费| 午夜福利视频1000在线观看| 成人亚洲欧美一区二区av| 听说在线观看完整版免费高清| av在线老鸭窝| 菩萨蛮人人尽说江南好唐韦庄| 国产精品国产三级国产专区5o| 一级毛片黄色毛片免费观看视频| 啦啦啦中文免费视频观看日本| a级一级毛片免费在线观看| 日韩不卡一区二区三区视频在线| 晚上一个人看的免费电影| 国产免费一级a男人的天堂| 69av精品久久久久久| kizo精华| 国产一区二区亚洲精品在线观看| 精品久久久噜噜| 日韩中字成人| 国产69精品久久久久777片| 亚洲欧美精品自产自拍| 亚洲va在线va天堂va国产| 精品少妇黑人巨大在线播放| 舔av片在线| 免费黄频网站在线观看国产| 亚洲综合色惰| 欧美成人午夜免费资源| 26uuu在线亚洲综合色| 国产精品美女特级片免费视频播放器| 日本-黄色视频高清免费观看| 国精品久久久久久国模美| 久久久精品免费免费高清| 国产精品国产三级国产av玫瑰| 国产精品伦人一区二区| 永久免费av网站大全| 91精品伊人久久大香线蕉| 国产伦一二天堂av在线观看| 国产精品爽爽va在线观看网站| 午夜精品一区二区三区免费看| 久久久久精品久久久久真实原创| 国产单亲对白刺激| 亚洲精品自拍成人| 国产美女午夜福利| 身体一侧抽搐| 国产精品久久视频播放| 看十八女毛片水多多多| 亚洲欧美日韩卡通动漫| 国内精品一区二区在线观看| 国产精品女同一区二区软件| 中文资源天堂在线| 欧美另类一区| 成人欧美大片| 少妇的逼好多水| 国产大屁股一区二区在线视频| 亚洲精品成人久久久久久| 麻豆精品久久久久久蜜桃| 永久免费av网站大全| 性色avwww在线观看| 免费无遮挡裸体视频| 18禁在线播放成人免费| 久久久久免费精品人妻一区二区| 久久久精品欧美日韩精品| 联通29元200g的流量卡| 亚洲熟妇中文字幕五十中出| 国产在线一区二区三区精| 日韩av不卡免费在线播放| 日本免费a在线| 日韩欧美国产在线观看| 亚洲最大成人av| 51国产日韩欧美| 免费看光身美女| 色吧在线观看| 国产精品国产三级国产专区5o| 国产毛片a区久久久久| 中国国产av一级| 国产欧美日韩精品一区二区| 国产一区二区亚洲精品在线观看| 成人欧美大片| 久久久精品94久久精品| 欧美潮喷喷水| 久久久久久久午夜电影| 80岁老熟妇乱子伦牲交| 亚洲欧洲日产国产| 少妇的逼水好多| 亚洲av福利一区| 久久久久久久久久久丰满| 男女下面进入的视频免费午夜| 久久99热6这里只有精品| 日韩av不卡免费在线播放| 日本欧美国产在线视频| 国产一级毛片七仙女欲春2| 能在线免费看毛片的网站| 亚洲成色77777| 一区二区三区四区激情视频| www.av在线官网国产| 亚洲av一区综合| 亚洲人成网站在线观看播放| 舔av片在线| 波多野结衣巨乳人妻| 天堂√8在线中文| 男女那种视频在线观看| 国产精品一区二区三区四区久久| 国产一区有黄有色的免费视频 | 久热久热在线精品观看| 国产真实伦视频高清在线观看| 麻豆精品久久久久久蜜桃| 亚洲激情五月婷婷啪啪| 国产精品美女特级片免费视频播放器| 午夜福利高清视频| 久久精品国产亚洲网站| 自拍偷自拍亚洲精品老妇| 非洲黑人性xxxx精品又粗又长| av网站免费在线观看视频 | 精品国产一区二区三区久久久樱花 | 你懂的网址亚洲精品在线观看| 美女内射精品一级片tv| 亚洲经典国产精华液单| 97热精品久久久久久| 亚洲最大成人中文| 亚洲国产精品成人综合色| 国内精品一区二区在线观看| 校园人妻丝袜中文字幕| 女人久久www免费人成看片| 一夜夜www| 亚洲最大成人中文| 丝袜美腿在线中文| 黄色日韩在线| 一本久久精品| 国产免费一级a男人的天堂| 一本一本综合久久| 日韩av不卡免费在线播放| 午夜爱爱视频在线播放| 亚洲精品久久久久久婷婷小说| 国产成人aa在线观看| 日韩av在线免费看完整版不卡| 亚洲国产色片| 日日啪夜夜撸| a级毛色黄片| 中文欧美无线码| 国产精品伦人一区二区| 少妇丰满av| 丝瓜视频免费看黄片| 日韩精品有码人妻一区| 在线观看人妻少妇| 2018国产大陆天天弄谢| 80岁老熟妇乱子伦牲交| 综合色丁香网| 99久久九九国产精品国产免费| 大片免费播放器 马上看| 精品少妇黑人巨大在线播放| 日韩av免费高清视频| 99热这里只有精品一区| 黄色日韩在线| 亚洲国产av新网站| 能在线免费观看的黄片| 久久精品国产亚洲av涩爱| 亚洲av男天堂| 成人二区视频| 国产一级毛片七仙女欲春2| av卡一久久| 国产伦一二天堂av在线观看| 黄片wwwwww| 简卡轻食公司| 欧美区成人在线视频| 99九九线精品视频在线观看视频| 久久久久久久大尺度免费视频| 国产高清不卡午夜福利| 国产成人福利小说| 欧美成人精品欧美一级黄| 亚洲第一区二区三区不卡| 久久97久久精品| 精品国内亚洲2022精品成人| 又大又黄又爽视频免费| 最近2019中文字幕mv第一页| 一个人看的www免费观看视频| 中国国产av一级| 成人一区二区视频在线观看| 草草在线视频免费看| 久久99热6这里只有精品| 永久免费av网站大全| 大片免费播放器 马上看| 波多野结衣巨乳人妻| 最近最新中文字幕免费大全7| 内地一区二区视频在线| 成人国产麻豆网| 老师上课跳d突然被开到最大视频| 菩萨蛮人人尽说江南好唐韦庄| 男女那种视频在线观看| 97在线视频观看| 麻豆成人av视频| 嫩草影院新地址| 免费无遮挡裸体视频| 日韩成人av中文字幕在线观看| 可以在线观看毛片的网站| 少妇被粗大猛烈的视频| 老司机影院成人| 人体艺术视频欧美日本| 丰满乱子伦码专区| 青春草视频在线免费观看| 精品久久久久久电影网| 能在线免费观看的黄片| 99re6热这里在线精品视频| 床上黄色一级片| 女的被弄到高潮叫床怎么办| 日韩一本色道免费dvd| 欧美 日韩 精品 国产| 日韩在线高清观看一区二区三区| 国产成人精品婷婷| 老师上课跳d突然被开到最大视频| 亚洲欧洲国产日韩| 免费看日本二区| 汤姆久久久久久久影院中文字幕 | 99久国产av精品| 国产精品国产三级专区第一集| 免费黄色在线免费观看| 91久久精品电影网| 日本欧美国产在线视频| 国产白丝娇喘喷水9色精品| 18禁在线播放成人免费| 人妻一区二区av| 亚洲av电影在线观看一区二区三区 | 最近2019中文字幕mv第一页| 国产精品99久久久久久久久| 免费大片18禁| 欧美激情国产日韩精品一区| 成人特级av手机在线观看| 亚洲三级黄色毛片| 国产精品久久久久久av不卡| 日韩成人伦理影院| 久久久精品欧美日韩精品| 97超碰精品成人国产| 亚洲最大成人av| 国产精品人妻久久久久久| 亚洲熟妇中文字幕五十中出| 美女高潮的动态| av播播在线观看一区| 99热6这里只有精品| 成人毛片60女人毛片免费| 国产精品熟女久久久久浪| av福利片在线观看| 午夜亚洲福利在线播放| 在线播放无遮挡| 亚洲欧洲日产国产| 国产淫语在线视频| 99热网站在线观看| 亚洲美女搞黄在线观看| 精华霜和精华液先用哪个| 99热全是精品| 亚洲精品亚洲一区二区| 人妻少妇偷人精品九色| 亚洲电影在线观看av| 成人无遮挡网站| 三级男女做爰猛烈吃奶摸视频| 男女视频在线观看网站免费| 日韩国内少妇激情av| 天美传媒精品一区二区| 日韩成人伦理影院| 日韩强制内射视频| 欧美变态另类bdsm刘玥| 日本猛色少妇xxxxx猛交久久| 亚洲在线自拍视频| 七月丁香在线播放| 国产乱人偷精品视频| 精品一区二区免费观看| 亚洲四区av| 插逼视频在线观看| 丰满少妇做爰视频| 美女脱内裤让男人舔精品视频| 欧美xxxx黑人xx丫x性爽| 亚洲经典国产精华液单| 欧美日韩国产mv在线观看视频 | 亚洲精品成人av观看孕妇| 国内少妇人妻偷人精品xxx网站| 久久久久精品性色| 男的添女的下面高潮视频| 麻豆成人午夜福利视频| 国产一级毛片七仙女欲春2| 国产老妇伦熟女老妇高清| 国产一级毛片七仙女欲春2| 亚洲欧美清纯卡通| 亚洲国产高清在线一区二区三| 欧美xxxx黑人xx丫x性爽| 国产有黄有色有爽视频| av卡一久久| 色综合色国产| 亚洲国产欧美人成| 99久久人妻综合| 草草在线视频免费看| 久久精品久久久久久久性| 永久网站在线| 亚洲高清免费不卡视频| 欧美不卡视频在线免费观看| 欧美成人a在线观看| 99久久九九国产精品国产免费| 一二三四中文在线观看免费高清| 国产毛片a区久久久久| 丝袜美腿在线中文| av天堂中文字幕网| 大片免费播放器 马上看| 99视频精品全部免费 在线| 亚洲最大成人手机在线| 1000部很黄的大片| 亚洲成人久久爱视频| 自拍偷自拍亚洲精品老妇| 国产单亲对白刺激| 在线观看一区二区三区| 亚洲av在线观看美女高潮| 亚洲伊人久久精品综合| 国产成人精品一,二区| 国产精品人妻久久久影院| 一级毛片aaaaaa免费看小| 激情五月婷婷亚洲| 看黄色毛片网站| 一夜夜www| 黄色配什么色好看| 丰满少妇做爰视频| 日本-黄色视频高清免费观看| 最近2019中文字幕mv第一页| 日韩精品青青久久久久久| 天堂俺去俺来也www色官网 | 69人妻影院| h日本视频在线播放| 国产精品熟女久久久久浪| 久久久久久九九精品二区国产| 国产中年淑女户外野战色| 97人妻精品一区二区三区麻豆| 精品99又大又爽又粗少妇毛片| 精品一区二区免费观看| 久久久久久久亚洲中文字幕| 欧美另类一区| 国产成人一区二区在线| 两个人视频免费观看高清| 美女脱内裤让男人舔精品视频| 日韩亚洲欧美综合| 午夜福利在线在线| 亚洲精品456在线播放app| 亚洲怡红院男人天堂| 亚洲在线自拍视频| 夫妻午夜视频| 免费看光身美女| 女人十人毛片免费观看3o分钟| 在线a可以看的网站| 亚洲av免费高清在线观看| av.在线天堂| 免费黄色在线免费观看| 美女大奶头视频| 天堂影院成人在线观看| 色吧在线观看| 亚洲av中文字字幕乱码综合| 日韩成人av中文字幕在线观看| h日本视频在线播放| 在现免费观看毛片| 亚洲av国产av综合av卡| 久久久久久久国产电影| 在线免费观看的www视频| 日韩欧美一区视频在线观看 | 国产一级毛片在线| 久久这里只有精品中国| 久久精品熟女亚洲av麻豆精品 | 嘟嘟电影网在线观看| 亚洲欧美成人综合另类久久久| 国产精品麻豆人妻色哟哟久久 | 精品久久久久久久人妻蜜臀av| 国产av国产精品国产| 九九在线视频观看精品| 18禁裸乳无遮挡免费网站照片| 男女啪啪激烈高潮av片|