Molecular dynamics studies of ion-neutral and surface collisions : from molecular ions in ion mobility to ESI droplets / vorgelegt von Michelle Rajkovic. Wuppertal, April 2026
Inhalt
- Statement
- 1 Background
- 2 Introduction to molecular dynamics simulations
- 2.1 Underlying principles
- 2.2 Numerical integration
- 2.2.1 Numerical requirements for molecular dynamics simulations
- 2.2.2 Explicit Euler
- 2.2.3 Leapfrog
- 2.2.4 Velocity Verlet
- 2.2.5 Runge-Kutta methods
- 2.2.6 Predictor-Corrector
- 2.3 System ensembles
- 2.4 Boundary conditions
- 2.5 Force fields
- 3 Modeling of ion mobility
- 3.1 Ion mobility
- 3.2 Field dependence
- 3.3 Collision models
- 3.4 Inelastic collisions with Borgnakke-Larsen method
- 4 Dynamics of the electrospray process
- 4.1 Overview of working principle
- 4.2 Droplet formation
- 4.3 Droplet shrinkage and ion release
- 4.4 Observed discrepancies with ESI models and consequences
- 4.5 Potential fragmentation processes
- 5 Simulation software
- 6 Simulation of gas-phase ion-neutral collisions of molecular ions
- 6.1 Motivation
- 6.2 Molecular dynamics based trajectory method
- 6.3 Ion-neutral collisions with monoatomic neutral gas
- 6.3.1 Standard simulation run
- 6.3.2 General trajectory characteristics
- 6.3.3 Collision radius scaling dependence
- 6.3.4 Collision cross section dependence
- 6.3.5 Pressure dependence
- 6.3.6 Temperature dependence
- 6.3.7 Force field parameter sensitivity
- 6.3.8 Prediction of ion mobilities
- 6.3.9 Parallelization efficiency
- 6.4 Introduction of nitrogen as neutral gas
- 6.4.1 Force field adaption
- 6.4.2 Numerical instabilities
- 6.4.3 Ion mobility dependencies
- 6.4.4 Prediction of ion mobilities
- 6.4.5 Rotations
- 6.5 Variable hard sphere model
- 6.6 Summary
- 7 Simulation of electrospray droplets in surface collisions in vacuum
- 7.1 Droplet construction
- 7.2 SID LAMMPS model
- 7.3 Simulations of frontal wall collisions
- 7.4 Simulations of slanted wall collisions
- 7.5 Droplet size variation
- 7.6 Force field sensitivity analysis
- 7.7 SID model for SIMION
- 8 Conclusion and Outlook
- Bibliography
- A Force field parameters
- B Mathematical derivations and formulas
- B.1 Parameter conversion between 12-6 Lennard-Jones and mod. Buckingham
- B.2 High field mobilities from 2TT
- B.3 Total potential function
- B.4 Force field functions
- B.5 Borgnakke-Larsen energy transfer function
- C Graphics
- D Code snippets