To study influence of external field on aflatoxin B₁ (AFB₁), density functional theory on level of 6-311G is utilized. Total energy, dipole moments, geometric parameters, energy gap and infrared spectra under different external fields (from 0 to 0.015 a.u.) are obtained, respectively. UV-Vis spectra absorption of AFB₁ and excitation states are calculated with time dependent density functional theory method. It shows that total energy increases, while dipole moment decreases. Molecular geometric parameter and energy gap are strongly dependent on increasing field intensity. Two ultraviolet absorption peaks of AFB₁ show reversed shifts. Excitation energies decrease, which indicates that AFB₁ molecule is unstable under external fields.

Density functional theory on level of B3LYP at 6-311++G(d,p) was used to calculate CCl₃F geometrical parameters, dipole moments, charge distribution and total energies of ground state of CCl₃F molecule under external electric fields(F=-0.025~0.025 a.u.). It shows that with decreasing of C-Cl band distance, charge distribution of Cl increases. Molecular geometric parameter and total energy are strongly dependent on increasing field intensity. IR vibrationt spectrum of CCl₃F molecule shows observable blue shift as electric field increased to F=-0.02 a.u.