Qhov Tseem Ceeb Qhov Sib Txawv - Unit Cell vs Primitive Cell
Unit cell ntawm lub lattice yog chav tsev me tshaj plaws uas sawv cev rau tag nrho cov khoom siv hauv lub cev siv lead ua thiab lawv cov kev npaj. Chav tsev cell yog qhov tsawg tshaj plaws rov ua dua chav tsev ntawm lub lattice. Ib lub cell qub yog qhov tsawg tshaj plaws ntawm lub cell ntawm lub lattice. Yog li ntawd, lub primitive cell yog ib hom unit cell. Qhov sib txawv tseem ceeb ntawm chav cell thiab cov xov tooj qub qub yog tias chav cell muaj parallelepiped geometry whereas 2D primitive cell muaj parallelogram geometry thiab 3D primitive cell muaj parallelepiped geometry.
Lub Cell yog dab tsi?
Unit cell yog pawg tsawg tshaj plaws ntawm cov atoms uas muaj tag nrho cov symmetry ntawm ib tug siv lead ua, thiab los ntawm tag nrho cov lattice tuaj yeem tsim los ntawm kev rov ua dua hauv peb qhov ntev. Yog li ntawd, chav tsev cell yog cov rov qab units ntawm crystal lattices.
Ib chav cell tau piav qhia siv cov kab lattice thiab cov ntsiab lus lattice. Lattice parameters yog qhov ntev ntawm cov npoo ntawm nit cell (muab los ntawm a, b thiab c cim) thiab cov ces kaum ntawm chav tsev cell (muab los ntawm α, β thiab γ cim). Cov ntsiab lus lattice yog atoms, molecules lossis ions los ntawm cov lattice yog ua los ntawm.
Unit cell muaj geometry hu ua parallelepiped (ib daim duab 3D tsim los ntawm 6 parallelograms). Qhov geometry no tau piav qhia los ntawm rau lub lattice parameters (hais saum toj no). Cov hauj lwm ntawm cov ntsiab lus lattice yog muab los ntawm fractional coordinates denoted los ntawm xi, yi thiab zi, uas yog ntsuas los ntawm qhov chaw siv. Raws li Auguste Bravais (1850), muaj 14 hom lattices, hu ua Bravais lattices. Cov chav tsev ntawm cov Bravais lattices yog raws li nram no.
Daim duab 1: Chav Cells ntawm 14 Bravais Lattices
Cov npe ntawm cov cell (1-14) hauv cov duab saum toj no tau muab hauv qab no. (Ntawm no, P yog hais txog "primitive centering", C yog hais txog "centered ntawm ib theem" thiab kuv yog hais txog "lub cev nruab nrab" whereas F yog hais txog "lub ntsej muag centered").
- Cubic P
- Cubic I
- Cubic F
- Tetragonal P
- Tetragonal I
- Orthorhombic P
- Orthorhombic C
- Orthorhombic kuv
- Orthorhombic F
- Monoclinic P
- Monoclinic C
- Triclinic
- Rhomboedral
- Hexagonal
Dab tsi yog Lub Cev Muaj Zog?
Ib lub hauv paus chiv keeb hauv chemistry yog qhov tsawg tshaj plaws ntawm lub cell ntawm lub lattice, muaj cov ntsiab lus lattice nkaus xwb ntawm txhua qhov ntawm nws yim vertices. Yog li ntawd, nws yog ib tug yooj yim daim ntawv ntawm chav tsev cell. Nws yog ib qho kev sawv cev ntawm lub lattice (ib lub tshuab siv lead ua) uas tuaj yeem siv los ua tus cwj pwm ntawm lub lattice. Yog li ntawd, lub primitive cell yog ib tug primitive unit. Cov xovtooj qub qub tuaj yeem kos rau hauv ob sab lossis peb-dimensional daim ntawv.
Muaj ob hom primitive cells: ob-dimensional primitive cells thiab peb-dimensional primitive cells. Ob-dimensional primitive cells yog parallelograms. Qhov no txhais tau tias, tuaj yeem muaj cov kaum sab xis, qhov ntev sib npaug lossis ob qho tib si hauv cov hlwb qub qub. Hom kab mob primitive muaj raws li hauv qab no.
Ib lub xov tooj peb-dimensional primitive cell paub tias yog parallelepiped (ib daim duab 3D tsim los ntawm 6 parallelograms). Nws muaj cov ces kaum orthogonal, sib npaug ntev los yog ob qho tib si. Hom peb-dimensional primitive cells muaj npe hauv qab no.
- Parallelepiped (Triclinic)
- Oblique rhombic prism (Monoclinic)
- Oblique rectangular prism (Monoclinic)
- Txoj cai rhombic prism (Orthorhombic)
- Rectangular cuboid (Orthorhombic)
- Square cuboid (Tetragonal)
- Trigonal trapezohedran (Rhombohedral)
- Cub (Cubic)
Dab tsi yog qhov txawv ntawm Unit Cell thiab Primitive Cell?
Unit Cell vs Primitive Cell |
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| Ib chav tsev cell yog pawg tsawg tshaj plaws ntawm cov atoms uas muaj tag nrho cov symmetry ntawm cov siv lead ua, thiab los ntawm tag nrho cov lattice tuaj yeem tsim los ntawm kev rov ua dua hauv peb qhov ntev. | Ib lub hauv paus chiv keeb hauv chemistry yog qhov tsawg tshaj plaws ntawm lub cell ntawm lub lattice, muaj cov ntsiab lus lattice ntawm txhua qhov ntawm nws yim vertices nkaus xwb. |
| geometry | |
| Unit cell muaj parallelepiped geometry. | 2D cov xov tooj qub qub muaj qhov sib luag geometry whereas 3D primitive cell muaj parallelepiped geometry. |
| Unit cell yog cov qauv peb sab. | Primitive cell tuaj yeem muab ua ob-seem qauv lossis peb-dimensional qauv. |
Summary – Unit Cell vs Primitive Cell
Ib lub xov tooj qub yog ib hom ntawm cov cell. Chav tsev ntawm tes yog qhov tsawg tshaj plaws rov ua dua chav tsev ntawm lub tshuab siv lead ua uas sawv cev rau cov qauv rov ua dua ntawm cov lattice. Qhov sib txawv tseem ceeb ntawm chav tsev cell thiab primitive cell yog tias chav tsev cell muaj parallelepiped geometry whereas 2D primitive cell muaj parallelogram geometry thiab 3D primitive cell muaj parallelepiped geometry.
