exercises:2014_uzh_molsim:h2o_diff
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exercise:mm_uzh:h2o_diff [2014/05/31 18:05] – talirz | exercises:2014_uzh_molsim:h2o_diff [2020/08/21 10:15] (current) – external edit 127.0.0.1 | ||
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When simulating liquids or solids under periodic boundary conditions, we are making two fundamental approximations: | When simulating liquids or solids under periodic boundary conditions, we are making two fundamental approximations: | ||
- | - We simulate an infinite system, thus neglecting the fact that any real-world system | + | - We simulate an infinite system, thus neglecting the fact that any real-world system |
- We impose the condition that the properties of the system under study repeat //exactly// from one simulation cell to the next. The quality of this approximation depends on the system under study and the quantity of interest. | - We impose the condition that the properties of the system under study repeat //exactly// from one simulation cell to the next. The quality of this approximation depends on the system under study and the quantity of interest. | ||
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- Plot $D_{PBC}$ as a function of $1/L$, where $L$ is the length of the edge of the simulation box. | - Plot $D_{PBC}$ as a function of $1/L$, where $L$ is the length of the edge of the simulation box. | ||
- Perform a linear fit of this curve to obtain the diffusion constant $D=D_{pbc}(L=\infty)$ | - Perform a linear fit of this curve to obtain the diffusion constant $D=D_{pbc}(L=\infty)$ | ||
- | - Use equation (12) in the article to calculate the viscosity $\eta$ from the slope of $D_{PBC}(L)$. | + | - Use equation (12) in the article to calculate the viscosity $\eta$ from the slope of $D_{PBC}(1/L)$. |
- Compare the results to the data in the paper. | - Compare the results to the data in the paper. | ||
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exercises/2014_uzh_molsim/h2o_diff.1401559527.txt.gz · Last modified: 2020/08/21 10:14 (external edit)