He taumahi pāngarau e whakaahua ana i te whanonga ngaru o te irahiko i roto i te rāpoi ngota. Ka taea te whakamahi i tēnei taumahi ki te tātai i ngā āhuatanga matū me ngā āhuatanga ōkiko pēnei i te tūponotanga ki te kimi i tētahi irahiko i roto i tētahi rohe motuhake. I whakaurua te kupu orbital e Robert S. Mulliken i te tau 1932 hei whakarāpopototanga mō te taumahi ngaru orbital kotahi-irahiko. I te taumata taketake, ka whakamahia te reira ki te whakaahua i te rohe o te mokowā i roto i nei te taumahi he whānuitanga nui. Ka hangaia ngā orbitals rāpoi ngota mā te whakakotahi i ngā orbitals ngota ngota atomika, i ngā orbitals hybrid rānei mai i ia ngota o te rāpoi ngota, i ētahi atu orbitals rāpoi ngota rānei mai i ngā rōpū ngota. Ka taea te tātai i te nui mā te whakamahi i ngā tikanga HartreeFour<unk>ck, i ngā tikanga ā-whakatau (SCF) rānei.
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