Asked by Anonymous

Calculate the surface energy of the (100) plane of niobium. The heat of atomization is 745 kJ/mol.

Express your answer in J/cm2.
Answered by ongrwa swenra
3.091 E -5 joules / square centimeter
Answered by marcia
I put the answer of ongrwa and it's WRONG
Answered by DrB
The enthalpy of atomization of nobium is 745 KJ/mole.

The energy per atom is = 745000/Avogadro Number = 1.2371305e-18 J/atom

In a BCC structure each atom has 8 neighbors. Then
The energy per bond is = 1.2371305e-18 / 8 = 1.5464132e-19 J/bond

Now in a (100) plane the atoms density per unit area is = 4 (1/4) / a * a = 1/a2

For Nobium a = (2*92.91 / 8.57 * Avogadro number)^(1/3) = 3.30210056e-8 cm

Then the atoms density is 9.1710574e+14 atoms/cm2

Finally:The broken bonds are 4 per UC then (half for each surface)
Surface energy (100) =1/2 * 4 * Atoms density * Bond Energy = 0.00028364488 J/cm2
Answered by Anon
it's wrong. why is it wrong?
Answered by dr who
incorrect because bond energy is off by a factor of two because at 8 per atom you count bonds twice.

and this is an mit 3.091 cheat. shame on you.
Answered by ivo
6.32 e -3, works. not sure why though
Answered by frodo
the internet knows more about what you are doing than you know yourself!
Answered by DrB
I don't know why it is wrong. But I'm sure about the answer.

The atoms you need broke on (100) plane are the four in the plane bonded to the body central atom (remember that each atom in a BCC Crystal has 8 neighbors but you only need broke 4 - if you broke the 8 bonds you atomize the crystal)
Answered by drb is a clueless jert
why you keep insisting? can you not read?

also, this is an exam question

cheater alert

boot this guy off the list
Answered by Anonymous
I think asking a question when you don't know how to solve it is the best thing one could do. Also, nobody should point fingers when somebody is cheating. It's their problem, not yours.

About the question...I can't solve it either. I looked for explanations. Couldn't find them.
Answered by cheat alert
folks, these are the simplest questions.

if you are unable to answer a question like this yourself, then you simply have not done the work you need to do to improve yourself to the level of "barely competent in the field".

perhaps less time worrying over how to get some anonymous idiot on the internet (who probably earned their credentials by cheating through online courses) to help you and more time on the target, which is improving by 'engaging the struggle'.
Answered by Anonymous
In case somebody will need this later, the answer is 7.12*10^-5 J/cm2.
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