[DFTB-Plus-User] Energy problem about H2 and H2O

[nlu at mail.ustc.edu.cn]

Dear everyone,
 I have using DFTB+ 1.0.1, and I have some doubts about the cluster energy in the result of autotest of H2O and H2. In the autotest of spin test, the total energy of H2 is -14.726823 eV, and the total energy of H2O is -101.594405 eV. My question is why the difference of total energy is so large (about 90 eV) for H2 and H2O, for they just have an O atom differnce?  Thanks for your attention, and hope to hear from you.  
                                                                         yours,
                                                                           Lu