Xenon Transport Simulation

Molecular Dynamics of Water, Xenon, and Zinc Membrane

Molecular Physics Computational Chemistry Data Visualization

Simulation Parameters

Adjust the number of molecules in the simulation:

Simulation Video

About This Simulation

This simulation models the transport of xenon gas through a zinc membrane, surrounded by water molecules. The process is governed by several key physical chemistry principles:

Bond Energy in Water Molecules

The O-H bonds in water are modeled using a harmonic potential:

\[ V_{bond}(r) = \frac{1}{2} k_{bond} (r - r_{eq})^2 \]

Where \(k_{bond} = 50000\) kJ/(mol·nm²) and \(r_{eq} = 0.09572\) nm.

H-O-H Angle in Water

The H-O-H angle is also modeled using a harmonic potential:

\[ V_{angle}(\theta) = \frac{1}{2} k_{angle} (\theta - \theta_{eq})^2 \]

Where \(k_{angle} = 500\) kJ/(mol·rad²) and \(\theta_{eq} = 104.52^{\circ}\) (1.8242 radians).

Coulombic Interactions

Electrostatic interactions are calculated using Coulomb's law:

\[ F_{coulomb} = k_e \frac{q_1 q_2}{r^2} \]

Where \(k_e = 138.9355\) kJ·nm/mol and charges are \(q_O = -0.834 e\), \(q_H = 0.417 e\), and \(q_{Xe} = -1 e\).

Velocity Verlet Integration

The simulation uses the Velocity Verlet algorithm to integrate the equations of motion:

\[ \mathbf{r}(t + \Delta t) = \mathbf{r}(t) + \mathbf{v}(t) \Delta t + \frac{1}{2} \mathbf{a}(t) \Delta t^2 \]

\[ \mathbf{v}(t + \Delta t) = \mathbf{v}(t) + \frac{1}{2}[\mathbf{a}(t) + \mathbf{a}(t + \Delta t)]\Delta t \]

Thermostat Control

Temperature control is implemented using a velocity rescaling thermostat, which scales velocities to maintain the target temperature:

\[ \lambda = \sqrt{\frac{T_{target}}{T_{current}}} \]

\[ \mathbf{v}_i \rightarrow \lambda \mathbf{v}_i \]

Key Components:

  • Water Molecules: Simulated with realistic O-H bond lengths and H-O-H angles
  • Xenon Atoms: Modeled as charged particles
  • Zinc Membrane: Fixed structure that presents a barrier for transport

Simulation Details:

  • Simulation Box Size: 40 nm³
  • Temperature: 300K
  • Integration Time Step: 0.001 ps
  • Bond Length (O-H): 0.09572 nm
  • Bond Angle (H-O-H): 104.52°
  • Force constants derived from quantum chemistry calculations

Physical Chemistry of Xenon Transport

Transport Mechanism

Xenon transport through the zinc membrane occurs via several mechanisms:

Xenon Transport Rate

The rate of xenon transport through the membrane can be approximated using a modified Arrhenius equation:

\[ \text{Rate} = A \cdot e^{-\frac{E_a}{RT}} \cdot C_{Xe} \cdot (1 - \theta) \]

Where \(E_a\) is the activation energy, \(C_{Xe}\) is xenon concentration, and \(\theta\) is the fractional occupancy of membrane sites.

Quantum Chemistry Foundations

The simulation parameters are derived from quantum chemistry calculations that provide:

  • Bond force constants from Hessian matrix eigenvalues
  • Atomic charges from Mulliken population analysis
  • Equilibrium geometries from energy minimization

These quantum-level calculations ensure accurate representation of molecular interactions and dynamics at the atomic scale.

Computational Methods

The simulation combines several computational approaches:

  • Molecular Dynamics: For time evolution of the system
  • Quantum Chemistry: For force field parameters
  • Statistical Mechanics: For temperature control and ensemble averaging

Energy Conservation

Total energy in the NVE ensemble should be conserved:

\[ E_{total} = E_{kinetic} + E_{potential} = \text{constant} \]

Small fluctuations may occur due to numerical integration and thermostat effects.