Optimization of long range potential interaction parameters in ion mobility spectrometry.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Analytical Chemistry

Background:

• Collision cross section (CCS) calculations are crucial for ion mobility spectrometry (IMS).
• Accurate Lennard-Jones (L-J) potential parameters are essential for reliable CCS predictions.
• Density Functional Theory (DFT) offers a computational approach for these calculations.

Purpose of the Study:

• To optimize Lennard-Jones (L-J) potential parameters for collision cross section (CCS) calculations in ion mobility spectrometry (IMS).
• To evaluate the accuracy of DFT-based CCS calculations using optimized L-J parameters.
• To investigate the relationship between L-J parameters and computational efficiency.

Main Methods:

• Experimental CCS data for 16 small organic molecules in N2 were compared to DFT calculations.
• The IMoS algorithm and a 4-6-12 potential were employed for CCS computations.
• A ceteris paribus optimization method was used to determine L-J potential parameters (σ and ϵ).

Main Results:

• Optimized L-J parameters are not unique, exhibiting an exponential relationship between intercept and well-depth.
• Certain molecules present challenges for L-J parameter optimization.
• Calculated CCS values showed an average deviation of only 1% from experimental data.

Conclusions:

• DFT calculations are viable for accurate CCS predictions in IMS.
• L-J parameters can implicitly account for effects like ion-quadrupole potential and diffuse scattering.
• This approach significantly improves computational efficiency without sacrificing accuracy.