AMBER Archive (2008)

Subject: AMBER: Explanation of the energy unit ?

From: Marek Malư (maly_at_sci.ujep.cz)
Date: Sat Sep 06 2008 - 09:29:06 CDT

  Dear Sirs,

  I have probably very trivial question. So trivial, that is almost
  impossible to find answer so I am sending direct question to the amber
mailing list.

  My question is "How to understand (interpret) energetical unit kcal/mol ?"

  Before I started some type of simulations I worked with usual energetical
units like

  "J", "cal" or "kcal", "eV" etc.

  When I started with molecular simulations (materials, live science) at
the atomistic level I found out
  that the most common unit is "kcal/mol" but I have a little problem with
its interpretation.

  Let's assume that we have some molecular system Y and we for example
  calculate the total energy of this system. Lets say that result is
X[kcal/mol].

  My only interpretation is that X is the energy in [kcal] of NA systems Y.
  So if I want energy of one system Y in [kcal] it is X/NA. Where NA is
  Avogadro constant.

  Am I right ? If not please could you explain how to interpret this unit
  resp. the numbers in this units ?

  What is the background of this unit ? Why aren't for example used eV
  etc. ?

  Thanks very much in advance for the clear explanation or at least for
  some relevant link !

  With best regards

       Marek Maly

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