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### Entropy at 0 K

Posted: Tue Feb 12, 2019 10:08 pm
Hello,

Is it possible to have 0 entropy? Also, what is the difference between residual, translational, vibrational, and transitional entropy?

Thanks

### Re: Entropy at 0 K

Posted: Tue Feb 12, 2019 10:11 pm
At 0K, if the structure is perfectly ordered, then entropy is equal to zero. However, if there are still possible microstates, the entropy will not be equal to zero.

### Re: Entropy at 0 K

Posted: Sat Feb 16, 2019 9:14 pm
It is only possible to have entropy equal to 0 if the temperature is equal to 0K and if the substance in question is perfectly ordered.

### Re: Entropy at 0 K

Posted: Mon Feb 18, 2019 10:49 pm
Hello.

when temperature reaches 0K, then entropy tends to zero. At 0K theoretically, a molecule/compound can still have positional entropy (number of micro-states). If it is perfectly ordered, then yes, entropy would theoretically be 0)

### Re: Entropy at 0 K

Posted: Tue Feb 19, 2019 11:47 am
When the entropy is at 0, it forms a perfect crystal. However, it still has some positional entropy. Higher entropy levels would result in higher rotational and vibrational entropy.

### Re: Entropy at 0 K

Posted: Tue Feb 19, 2019 11:56 am
The last 3 types of entropy you mentioned relate to the position and possible movement available to a molecule. The first type you mentioned, residual, relates to the residual entropy left in a molecule when it is at 0 K. At that point there is no entropy due to movement, but if the molecule has more than one possible position at 0 K then it will have residual entropy, which is why not all molecules will be at 0 entropy at 0 K.

### Re: Entropy at 0 K

Posted: Tue Feb 19, 2019 12:41 pm
Its possible to have 0 entropy, when there is no degeneracy at absolute zero. At higher temperatures, vibrational, translational, transitional entropy are spontaneous and add to the total entropy. This is why we have been considering entropy at 0 K because then the S= K In(W) holds true (does not include other types of entropy). Hope this helps :)