Chapter 9: More on Thermostats Flashcards Preview

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Flashcards in Chapter 9: More on Thermostats Deck (5):
1

Andersen Thermostat 
(Overview)

  • system stochastically coupled to heat bath at frequency ν
    • selected particle experience collisions with frequency ν
    • move system from one constant energy shell to another
  • collisions uncorrelated → distribution of ∆t between collisions is Poisson process

2

Andersen Thermostat 
(Algorithm)

  1. Initial conditions {rN(0),pN(0)} → integrate for ∆t
  2. Select particles with probability νto collide with heat bath
  3. Selected particles get velocity drawn from Boltzmann distribution

3

Andersen Thermostat 
(Notes)

  • stochastic collisions disturb dunamics → bad for measuring dynamic properties
  • static properties are unaffected

4

Nosé-Hoover Thermostat 
(Overview)

  • extended Lagrangian approach
  • deterministic equations of motion
  • sQ parameters couple system to virtual reservoirr by extending degrees of freedom
  • certain choice are made (Nosé-Hoover formalismL = 3N) gives 

5

Nosé-Hoover Thermostat 
(Notes)

  • → ∞ gives microcanonical ensemble
  • smooth, deterministic, time-reversible, but nearly periodic temperature fluctuations
  • NVE safest for dunamic propertoes