[CPMD-list] What are classic energies for CP MD and PI MD?

[Lan-Feng Yuan (lyuan@Princeton.EDU)]

  Dear CPMD community,

  I am using CPMD to do path integral simulations and find it very useful, thanks! The total quantum energy in output corresponds to the total energy estimator, and by subtracting the nuclear ground state energy, I can get the vibrational energy at a given temperature. Well, what is the "ECLASSIC" in output? Also, in a classic CP MD simulation, "ECLASSIC" is also printed. Are they the same thing? I guess it's the sum of Kohn-Sham energy and classic nuclear kinetic energy (which is proportional to instant temperature). If this is correct, then ECLASSIC - EKS  should be equal to 3/2*N*k_B*T (N is number of atoms) when average temperature reaches its target value, right? However, it seems that I never get it exact. What's the problem? Thank you very much! 

  Best regards,

  Lan-Feng

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Dr. Lan-Feng Yuan,
Postdoctoral Associate,
Department of Chemistry,
Princeton University,
Princeton, NJ 08544, USA
Office Phone: 1-609-258-1834
Fax: 1-609-258-6746
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