Physical Chemistry> What is the difference between hcp and cc...

What is the difference between hcp and ccp packing??

Shreyas Patil , 9 Years ago

Grade 12

3 Answers

SAHIL

Covering the tetrahedral voids: Here, tetrahedral voids of the second layer may be covered by the spheres of the third layer. It gives rise to ABABAB… type pattern. The three-dimensional structure is called hexagonal close-packed structure. Examples: Mg, Zn
Covering the octahedral voids: Here, octahedral voids of the second layer may be covered by the spheres of the third layer. It gives rise to ABCABCABC… type pattern. The three-dimensional structure is called cubic close-packed structure or face-centred cubic structure. Examples: Cu, Ag
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Last Activity: 9 Years ago

Shreyas Patil

Last Activity: 9 Years ago

Umakant biswal

@ shreyas
there are a small besic diffrence between the two types of packing , i am explaining that below .
HCP (HEXAGONAL CLOSE PACKING )
1- HERE , the third layer of sphere are exactly identical with the first layer of sphere . that means the spheres are alligned in ABAB PATTERN , TAKE A AS FRST LAYER SPHERE ARRENGEMENT , AND B AS THE 2ND LAYER SPHERE ARRENGEMENT .
2- IT COVERS THE TETRAHEDRAL VOID , TETRAHEDRAL VOID ARE THE FALSE VOIDS . THAT WILL GENERATE IF THE SPHERE WILL ALLIGN ON THE NEXT LAYER OF VOID .
3- ITS ONE OF THE IDEAL WAY OF PACKING , AND THE PACKING FRACTION IS APPROXIMATELY 74 PERCENT .
CCP (CUBIC CLOSE PACKING )
1-HERE , the fourth layer sphere are same as that of the frst layer , the same sequence , take A as frst layer arrengement , B as 2^nd layer arrengement , and C as 3^rd layer arrengement .
2- its represented by ABCABC TYPE , (REASON EXPLAINED ABOVE )
3- IT will cover the octahedral voids , the octahedral voids are the true voids , and these will be generate when a void will overlap with anathor void ,
(REMEMBER ITS DIFFRENT FROM TETRAHEDRAL , IN TETRAHEDRAL WE HAVE SPHERE OVERLAPPING A VOID)
4- ITS the less efficient packing than hcp one , with approx 68 percent packing efficiency ..
HOPE IT CLEARS YOUR DOUBT
ALL THE BEST ..