The geometries of AX_m(A=C,Si;X=H,F,Cl,Br,I ;m≤4) molecules are optimized by means of AM1 method,respectively.The EHOMO,ELUMO and the standard molar heats of formation are obtained.I t is found that linear relationship between observed maximum wavelengths of absorptions and the energy differences of the frontier orbital is well.At the same time,the standard molar heats of formation of these ...