3D MD Portable Simulator

The MolRun is the 3D classical mechanics simulator with ball-rod molecules model

Download:
MolRun.pdf

Molecular mechanics concern variety parts of physics and mathematics: classical mechanics and kinetics, thermodynamics, statistical physics, vector and tensor algebra, linear algebra and geometry, the theory of differential equations, and finally, the theory of numerical methods. This description is an invitation to follow the same path that the author did, to perceive the theoretical material necessary for molecular dynamics simulation.

MolRunManual.pdf -- MD5 checksum value: 25401f47921260114e2dce0f44878146

MolRun.zip

The MolRun program runs under the Windows OS, it is made the portable style, does not require installation.

MolRun.zip -- MD5 checksum value: cad5a368fecc2ebbe75d42c87ee103d6

Brief View

The program includes algorithms that can be grouped as follows.

The physical modeling algorithms: numerical integration of Newton's and Euler's equations, an algorithm for calculating the principal values and principal axes of the inertia tensor, an algorithm for calculating physical average values, an algorithm for calculating the volume given by an irregular set of points, a cluster search algorithm.

The visualizing of 3D world algorithms: an algorithm for constructing a central projection on an arbitrary plane, an algorithm for triangulating a surface, a ray tracing algorithm for a sphere and a plane element, an algorithm for a video file creating.

The superstructure algorithms: thermostat algorithm, barostat algorithm, a series of calculation supervisor, a three-dimensional molecular editor.

Some results

First step, full energy conservation test (with music ☺)

Molecular fantasy.

The molecular geometry shown on the picture, one atom has positive charge σ, the other has negative charge σ/2. σ=1.0, l=0.3, α=25° Atom-atom potential parameters: ε=0.046, α=5.0, rm=0.56.

Molecules: 50;
Video stream: 0.5 nS/frame;
Cube length: 8 nm;
Cooling: 10 nS mixing; 50 nS multiplicate all velocities 0.9999 per 1.0 nS; 240 nS constant energy.


3amg1.zip more video

Heat capacity.

If the system is heated at a constant rate, then it can be assumed that the internal energy and temperature of the system will increase linearly \(E(t) = E_0 + K_E t\) and \(T(t) = T_0 + K_T t\). Then, we obtain an expression for the heat capacity \(C_V = \left( \dfrac{\partial E}{\partial T} \right)_V = \dfrac{\partial E}{\partial t} \left. \right/ \dfrac{\partial T}{\partial t} = \dfrac{K_E}{K_T} \) recalculating to [Jxmol-1xK-1] we get 12,581 vs standard value 12,555 for Helium.

Heat capacity.

A more standard way to calculate the heat capacity is to measure the mean square of energy fluctuations \({\left\langle {\delta {E_k^2}} \right\rangle _{NVE}} = {k_b}{T^2}{C_V}\), recalculating the average value to the NVT ensemble gives the value of 12.586 [Jxmol-1xK-1] for Helium.

Harmonic confinement.

The harmonic confinement to impose the particles to gather into a single cluster, the volume of cluster calculated by Convex Hull algorithm. But the system like this is non-homogenous, so the pressure or other thermodynamic values calculation are open for discussion question.

Detailed discussion see:
Chemical Physics 580 (2024) 112219

A.V. Nazarkin, T.V. Shtelmakh Xenon condensation in a harmonic confinement


Xenon150.zip more video

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