Electronic and Structural Properties of Bialkali Antimonide Photocathode Materials

Electronic band structure theories took a great leap with the introduction of density functional theory into quantum mechanics. Later so many methods emerged out of it and one of the successful methods is the Linear Mu n-Tin Orbital theory with Atomic Sphere Approximation.В This is a first principle approach to the electronic srtucture problemwhich is simple, transparent, elegant and fastВ . This metho d is used to study the electronic structure of bialkali antimonide photocathode materials.The e ect of pressure on these materials is studied by using the Murnaghan equation of state

Results

The band structure and the density of states for the three compoundsВ В В  aВ В  are dipicted below. The significant featureof the band sructure of these compounds is that the valence band is comprised of two sub-bands separated by a large gap of about 6 . This implies that these compounds have chemical bonds of highly ionic nature.

THe bulk modulus values of these materials show that they can easily be compressed and one can expect a structural transi-tion under moderate pressures. Comparing the band structures and density of states with the correspond-ing В binary compounds likeВ andВ В it is clear that the presence ofВ В the new alkali atom causes the 5 states to contribute to the conduction band.В If the new alkali atom has very less electro negativity then its contribution will be very high to change the binary material structure. The experimental bandgap ofВ В В В В В В В В  is 1 1В hich reduces to 0.95В В  inВ В  and the experimental bandgap ofВ В В  is 0 9В В В which re-duces to 0 52 and 0 66 inВ В andВ В В В espectively. Thus the presence of extra alkali atom tries to reduce the band gap.

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