md-ex05 - by(a Running it with the test input For 10 ps...

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Molecular Dynamics Simulations 2011. Exercise 5: mdmorse : Cal- culating the forces. Return by Tue 11.10. at 12:15, exercise session Thu 13.10. at 12:15. 1. (12 p) Write the subroutine GetForces() in the fle forces.f90/.c in mdmorse . The subroutine should calculate the interaction between atoms with the Morse potential using the input parameters morseD , morsealpha , and morser0 , which are the parameters oF the potential. Use the neighbor list created previously. The resulting subroutine should output the accelera- tions in the array a(i) and the potential energies in the array Epot(i) . The units are as described in main.f90/.c . 2. (8 p) Using subroutines written For the previous exercises (your own or the o±cial solutions on the web page) and the GetForces() subroutine, you should now have a working MD code. Demonstrate that the code works
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Unformatted text preview: by (a) Running it with the test input For 10 ps. AFter the intial 50 Fs, the total energy (column 6 oF the “ec” output lines) should ²uctuate or driFt less than 0.01 eV over 10 ps with a time step deltat oF 2 Fs. The temperature (column 3) should ²uctuate less than about 100 K around the average oF 300 K. (b) Running it as above, but with a Free surFace in all dimensions. Now the temperature and energy will be di³erent, but the total energy should still be conserved within about 0.02 eV aFter the frst 1 ps. Describe what happens. Return the exercise as the fle forces.f90 and a plot oF the total energy vs. time and the temperature vs. time For cases (a) and (b). AFter passing these tests, your code is probably correct. But you can never be absolutely sure. .....
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