md-ex06 - 2(10 p Implement Berendsen temperature control...

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Molecular Dynamics Simulations 2011. Exercise 6: Temperature control. Return by Tue 18.10. at 12:15, exercise session Thu 20.10. at 12:15. 1. (10 p) Using mdmorse , investigate the velocity distribution of the Cu atoms at 300 K. Make a histogram of the velocities obtained, and compare with the analytical Maxwell-Boltzmann distribution (see e.g. Mandl, Sta- tistical Physics, 2nd edition, eq. 7.59a). Plot the simulated and analytical distribution in the same Fgure, using both a linear and a logarithmic scale on the y -axis. Comment on the agreement of the two distributions. Hint: Use the actual (rather than desired) temperature of your simulation run in the comparison. Return the requested plots along with the answer to the question.
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Unformatted text preview: 2. (10 p) Implement Berendsen temperature control into mdmorse . Use the read-in parameters btctau and desiredT for this. The Frst one is the tem-perature control time constant and the second one the desired temperature towards which the temperature is scaled. Implement the algorithm so that no control is performed if btctau=0 . Test the control by simulating morse Cu with otherwise the default inputs but using desiredT=0.0 , initialT=300.0 , and btctau=1000.0 . How long does it take until the cell temperature has decreased to below 10 K? How about when running with btctau=100.0 ? Return the modiFed subroutines and answers to the questions....
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