Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field.

Weimin Gao,Lingxue Kong,Haitao Niu,Xungai Wang,Tong Lin

doi:10.1063/1.4861893

Abstract

The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform external electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.

Highlights

N,N-dimethylformamide (DMF) is a commonly used solvent and in applications, such as electrospinning1 and electric field assisted assembly of nanomaterials,2,3 it works under an externally applied electric or magnetic field, for example, for electrospinning with needle spinnerets an electric field of about more than 0.01 V/nm at the tip of the needles is generally used
The polarization of a molecule greatly relies on its position and surrounding environment, which is not a surprise considering that in the interactive atomic dipole induction scheme the induced dipole at each polarizable site is submitted to the permanent multipoles and induced dipoles of itself and other atoms, and considering the difference in the orientation of molecules with respect to the direction of external electric field being applied to the system
We extend the AMOEBA polarizable force field to include these interactions

Summary

INTRODUCTION

N,N-dimethylformamide (DMF) is a commonly used solvent and in applications, such as electrospinning and electric field assisted assembly of nanomaterials, it works under an externally applied electric or magnetic field, for example, for electrospinning with needle spinnerets an electric field of about more than 0.01 V/nm at the tip of the needles is generally used. There is little study to test its reliability in predicting the physical properties and structure of amides and other molecules under strong external field, the main advantage of the PIPF model over fixed point charge models, OPLS and OPLS-AA, to be claimed is its ability to provide information about the polarization effects among the molecules in liquid systems. Another polarizable force field that includes those parameters for various amides is the AMOEBA (Atomic Multipole Optimized Energetics for Biomolecular Applications).. The structure of liquid DMF under different external electric fields is characterized by its local molecule order and molecule orientation

SIMULATION DETAILS

Polarization

Pair correlation functions

Angle distribution density

Thermodynamic properties

CONCLUSIONS