Abstract:

Using density functional B3LYP and timedependent density functional theory (TDDFT), the author obtained the ground states dipole moment and total energy of αalanine molecule under different external electric fields (-0.015—0.005) at the 631+G(d,p) basis set level, and studied the influence of excitation energies Δ E and oscillator strengths f under the same external electric fields. The results show that the dipole moment of molecule first decreases and then increases sharply with the increase of electric field strength. The total energy of the molecule is -323.773 9 when there is no electric field. The total molecular energy increases with the increase of the electric field intensity, the total energy of the molecule reaches the maximum -323.771 5 as F=0.005. The excitation energies Δ E decreases with the increase of the electric field intensity, indicating that the αalanine molecule is easy to form excited state under the action of electric field.

Key words: α-alanine, electric field, excited state； timedependent density functional theory(TD-DFT)