Write the electronic Hamiltonian operator, h, in atomic units for the S atom, H2", 02-, He2+ and CH4. (11 marks) (b) (i) Explain the naming convention for the acronym 4-31++G(d,p). (5 marks) (ii) Name and discuss the main idea behind the oldest density functional. (3 marks) (iii) Explain the key idea behind the Kohn-Sham method. (3 marks) Write the electronic Hamiltonian operator, h, in atomic units for the S atom, H2", 02-, He2+ and CH4. (11 marks) (b) (i) Explain the naming convention for the acronym 4-31++G(d,p). (5 marks) (ii) Name and discuss the main idea behind the oldest density functional. (3 marks) (iii) Explain the key idea behind the Kohn-Sham method