USTC 2016 CASTEP / MS Mid-term Exam

(atoms and molecules)

(1) Using different exchange orrelation functional LDA and GGA-PBE, compare the bond energy of ground state paramagnetc, i.e., triplet, state of O₂ molecule.

 

(bond order)

(2) Based on the trend of C₂H₆ 、C₂H₄、C₂H₂ , analyse and compare the bond order of C₂ and N₂ .

 

(BS n PDOS)

(3) Band gap read out from DOS is the same as band gap read out from band structure calculaions. Why that happen ? and how to solve it ?

 

(advanced BS)

(4) Build and geometry-optimize an 8 atom cubic Al₃GaN₄ cell, this is equivalent to Al_0.75Ga_0.25N in Zinc Blende (ZnS) structure. Draw the wavefunction of this cell which correspond to the lowest unoccupied band of Gamma point of the primitive cell.

 

(magnetism)

(5) Why iron core is needed to make an electro-magnet ? Analyze magnetic moments of Mn, Fe, Co, Ni under low temperature. (materials demagnetized under high temperature, so we restrict our discussion to low temperature condition.)