Qhov Tseem Ceeb - BCC vs FCC
Cov ntsiab lus BCC thiab FCC yog siv los sau npe ob qhov sib txawv ntawm cov qauv crystalline. BCC stands rau lub cev-centred cubic qauv whereas FCC stands rau lub ntsej muag-centred cubic qauv. Cov no yog cov qauv ntawm cubic lattices. Yog li ntawd, cov kev npaj no muaj spheres (atoms, molecule los yog ions los ntawm cov lattice yog ua los ntawm) teem nyob rau hauv cubic lug. Chav tsev cell ntawm BCC muaj spheres nyob rau hauv cov ces kaum ntawm ib lub voos xwmfab thiab ib tug kheej kheej nyob rau hauv nruab nrab ntawm lub voos xwmfab. Txij li thaum muaj yim lub kaum rau hauv ib lub voos xwmfab, tag nrho cov spheres tam sim no nyob rau hauv BCC chav tsev cell yog 9. Chav tsev cell ntawm FCC muaj spheres nyob rau hauv txhua lub ces kaum ntawm ib lub voos xwmfab thiab tseem nyob rau hauv nruab nrab ntawm txhua lub cubic lub ntsej muag. Tom qab ntawd lub cell ntawm FCC muaj 12 spheres. Qhov sib txawv tseem ceeb ntawm BCC thiab FCC yog qhov kev sib koom tes ntawm BCC yog 8 qhov kev sib koom tes ntawm FCC yog 12.
BCC yog dab tsi?
Lo lus BCC sawv cev rau lub cev-chaw ua haujlwm cubic ntawm spheres (atoms, molecule lossis ions los ntawm cov lattice los ntawm). Nyob rau hauv qhov kev npaj no, spheres nyob rau hauv txhua lub ces kaum ntawm ib lub voos xwmfab thiab ib tug kheej kheej nyob rau hauv nruab nrab ntawm lub voos xwmfab. Ib chav tsev ntawm lub lattice yog qhov tsawg tshaj plaws chav tsev uas zoo li tag nrho cov qauv ntawm lub lattice. Txij li thaum ib lub voos xwmfab muaj 8 lub ces kaum, muaj tag nrho ntawm 9 spheres nyob rau hauv ib tug BCC qauv (yim nyob rau hauv lub ces kaum ntxiv rau nyob rau hauv nruab nrab).
Txawm li cas los xij, txhua tus kheej nyob rau hauv kaum ntawm chav tsev ntawm BCC yog ib tus tswv cuab ntawm chav nyob sib ze. Qhov ntawd yog vim lub lattice yog ua los ntawm ntau lub cell uas ntim ua ke. Txij li thaum muaj 8 spheres nyob rau hauv ib chav tsev cell uas yog cov ces kaum ntawm lwm chav tsev cell, tus naj npawb ntawm kev sib koom tes ntawm cov qauv BCC paub tias yog 8. Tom qab ntawd, thaum txiav txim siab tag nrho cov spheres hauv BCC chav tsev cell, nws muaj 2 spheres vim tias ib lub ces kaum muaj 1/8th ntawm spheres. Lub yim lub ces kaum ua ke ua ib tug kheej kheej, thiab muaj ib tug kheej kheej nyob rau hauv nruab nrab, ua ke nrog ua nyob rau hauv ob spheres.
Daim duab 01: BCC Structure
Kev ntim cov spheres hauv BCC kev npaj tsis nruj. Qhov ntawd txhais tau hais tias kev ntim khoom ntawm spheres hauv BCC tsis yog qhov ntim ze li hauv FCC (lub ntsej muag-centred cubic) lossis HCP (hexagonal close packing). Cov khoom ntim ntawm BCC yog 0.68. Packing factor yog qhov ntim ntawm spheres ib qhov ntim ntawm chav tsev cell. Piv txwv ntawm cov hlau uas muaj BCC qauv muaj xws li Lithium (Li), Sodium (Na), Potassium (K), Chromium (Cr) thiab Barium (Ba).
FCC yog dab tsi?
Lub sij hawm FCC sawv cev rau lub ntsej muag-centered cubic kev npaj ntawm spheres. Hauv qhov kev npaj no, cov spheres nyob rau hauv txhua lub ces kaum ntawm ib lub voos xwmfab (unit cell) thiab nyob rau hauv qhov chaw ntawm txhua lub ntsej muag cubic. Ntawm no kuj, txhua tus kheej kheej nyob rau hauv cov ces kaum yog ib tug tswv cuab ntawm cov nyob sib ze unit cell. Tsis tas li ntawd, txhua qhov chaw nyob hauv nruab nrab ntawm lub ntsej muag cubic tau koom nrog lub cell uas nyob ib sab.
Daim duab 2: FCC Structure
Tus naj npawb ntawm FCC yog 12. Qhov ntawd yog vim muaj 12 spheres ib chav cell uas tau koom nrog lwm lub cell. Cov net tag nrho ntawm spheres tam sim no nyob rau hauv FCC unit cell yog 4. Nws tuaj yeem suav tau raws li hauv qab no.
Total spheres in fab=(1/8) x 8=1
Total spheres in cubic faces=(1/2) x 6=3
Tom qab ntawd tag nrho cov spheres ib chav cell=1 + 3=4
Cov qauv FCC muaj ntau qhov ntim ntawm spheres dua li ntawm BCC (cov spheres ntim ze dua ua ke). Cov khoom ntim ntawm FCC qauv yog 0.74. Qhov no txhais tau hais tias qhov sib piv ntawm qhov ntim nyob ntawm spheres thiab tag nrho cov ntim ntawm chav tsev cell yog 0.74. Qee qhov piv txwv ntawm cov hlau uas muaj FCC qauv yog Aluminium (Al), Copper (Cu), Kub (Au), Lead (Pb) thiab Nickel (Ni).
Dab tsi zoo sib xws ntawm BCC thiab FCC?
- Ob leeg BCC thiab FCC yog cov qauv ntawm kev npaj ntawm cov lattices.
- Chav cell ntawm BCC thiab FCC cov qauv yog lub voos xwmfab.
Qhov txawv ntawm BCC thiab FCC yog dab tsi?
BCC vs FCC |
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| Lub sij hawm BCC stands rau lub cev-centered cubic kev npaj ntawm spheres (atoms, molecule los yog ions los ntawm cov lattice yog ua los ntawm). | Lub sij hawm FCC sawv cev rau lub ntsej muag-centred cubic kev npaj ntawm spheres. |
| Npaj Spheres | |
| BCC muaj spheres nyob rau yim kaum ntawm lub voos xwmfab thiab ib tug kheej kheej nyob rau hauv nruab nrab ntawm lub voos xwmfab. | FCC muaj spheres nyob rau yim lub kaum ntawm lub voos xwmfab thiab tseem nyob rau hauv qhov chaw ntawm lub cubic ntsej muag. |
| Tus lej | |
| Tus lej sib koom ua ke ntawm BCC qauv yog 8. | Tus naj npawb ntawm kev sib koom tes ntawm FCC qauv yog 12. |
| Packing Factor | |
| Cov khoom ntim ntawm BCC yog 0.68 | Cov khoom ntim ntawm FCC yog 0.74 |
| Number of Spheres in a Unit Cell | |
| Ib chav tsev ntawm BCC muaj tag nrho ntawm 2 spheres. | Ib chav tsev ntawm FCC muaj tag nrho ntawm 4 spheres. |
| Examples | |
| Qee yam piv txwv ntawm cov hlau uas muaj BCC qauv muaj xws li Lithium (Li), Sodium (Na), Potassium (K), Chromium (Cr) thiab Barium (Ba). | Qee yam piv txwv ntawm cov hlau uas muaj FCC qauv yog Aluminium (Al), tooj liab (Cu), Kub (Au), Lead (Pb) thiab Nickel (Ni). |
Summary – BCC vs FCC
BCC sawv cev rau lub cev-centred cubic arrangement. FCC sawv cev rau lub ntsej muag-centred cubic arrangement. Cov kev npaj no yog siv los piav qhia qhov chaw ntawm atoms, molecules lossis ions thiab qhov chaw khoob uas muaj nyob hauv cov qauv lattice. Qhov txawv ntawm BCC thiab FCC yog qhov kev sib koom tes ntawm BCC yog 8 qhov kev sib koom tes ntawm FCC yog 12.
