elastic modulus by ReaxFF

I try to calculated the elastic constant of pure aluminium and pure alumina by ReaxFF.

Compared with result from experiment, the elastic constants are almost the same when material is aluminium. But value of elastic constants calculated with ReaxFF are almost half of the consequence by experiments.
I get confused…
My Lmps version is April2 2011.

Any suggestions here?

Thanks!

2011/5/7 meihai3166 <[email protected]>:

I try to calculated the elastic constant of pure aluminium and pure alumina
by ReaxFF.

Compared with result from experiment, the elastic constants are almost the
same when material is aluminium. But value of elastic constants
calculated with ReaxFF are almost half of the consequence by experiments.
I get confused...

why confused? have you checked if the parameters you have
used were generated to reproduce those properties?

force fields are always compromises.

axel.

2011/5/7 meihai3166 <[email protected]>:

I try to calculated the elastic constant of pure aluminium and pure alumina
by ReaxFF.

Compared with result from experiment, the elastic constants are almost the
same when material is aluminium. But value of elastic constants
calculated with ReaxFF are almost half of the consequence by experiments.
I get confused...

why confused? have you checked if the parameters you have
used were generated to reproduce those properties?

force fields are always compromises.

axel.