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The potential energy surfaces of the halogen models X1-X2...NH3 and X-H...NH3 hydrogen bond models are investigated by the high level MP2 method with aug-cc-pVTZ basis (aug-cc-pVTZ-pp for bromine and iodine).The bond length and bond angle dependence are deeply analyzed.The bond angle influence is decreased as the bond length increased.Comparatively,the bottom of the potential well for the HB models is much flatter than that for the XB models,which indicated that the angle dependence in the XB models is much smaller than that in the HB models.As the bond length increased,the potential energy curve of the XB models is more and more similar to that of the HB models.According to the AMBER calculations,it is shown that the extra-point charge force field is not appropriate to descript this type of halogen bond.