دراسة انماط الاهتزاز وبعض خصائص جزيئة الفورمالديهايد H2CO باستعمال طريقة Ab-initio

Abstract

In this research we study vibration modes of Formaldehyde molecule theortically by using restricted ab-initio methods.geometry optimization of the Formaldehyde was obtained depending on the Hartree- Fock (rhf) equation for restricted system by using STO - 3G basis sets.The eigen value was studied , as well as the molecular orbital calculation and energy level diagram appears that paired electron . The modes of vibrationes were calculated under the steady state geometry condition and presented in graphically with frequency,intensity and symmetry for each mode.Final level HOMO and energy value EHOMO = -9.642789 eV while symmetry of this level was 2B2 ,and the first LUMO with energy value ELUMO = 7.676093 eV with symmetry 2B1. The absolute value of the final level HOMO gives the Ionization potential which is equal to (9.642789 eV) , while the first level LUMO represnt electron affinity which is equal to (7.676093) eV , and the Fermi level energy is equal to 17.318882 eVThe total energy of Formaldehyde equal to (-3057.151742 eV) where calculated by Ab-initio method compared with different semi-empirical methods, and we represente the electrostatic potential and charge density distribution in 2D,3D.