Microcanonical ensemble

Ensemble variables

(One component system, 3-dimensional system, ... ):

• $\left.N\right.$: Number of Particles

• $\left.V\right.$: Volume

• $\left.E\right.$: Internal energy (kinetic + potential)

Partition function

$Q_{NVE}={\frac {1}{h^{3N}N!}}\int \int d(p)^{3N}d(q)^{3N}\delta (H(p,q)-E).$

where:

• $\left.h\right.$ is the Planck constant

• $\left(q\right)^{3N}$ represents the 3N Cartesian position coordinates.

• $\left(p\right)^{3N}$ represents the 3N momenta.

• $H\left(p,q\right)$ represent the Hamiltonian, i.e. the total energy of the system as a function of coordinates and momenta.

• $\delta \left(x\right)$ is the Dirac delta distribution

Thermodynamics

$\left.S=k_{B}\log Q_{NVE}\right.$

where:

• Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \left. S \right. } is the entropy.

• Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \left. k_B \right. } is the Boltzmann constant

References

1. D. Frenkel and B. Smit, "Understanding Molecular Simulation: From Algorithms to Applications", Academic Press