1. A DFT photoemission analysis
Photocathode Physics for Photoinjectors (P3) 2016
Jefferson Laboratory, October 17-19, 2016
UIC
HCP elemental metals:
A DFT photoemission analysis
W. Andreas Schroeder
Physics Department
University of Illinois at Chicago
Tuo Li
Benjamin Rickman
National Science Foundation
PHYS

2. UIC HCP Brillouin zone TWO primary crystal emission faces: (0001)
(1000)
(0110) A M L  K H
TWO primary crystal emission faces:
(0001)-face
[basal-plane emission]
   A direction
(1010)-face
   K direction -
Band structure display convention: -M-K--A-L-H-A | L-M | K-H

3. UIC DFT results: Work functions
− Thin-slab method (0.05eV uncertainty)
Metal
(0001) (eV)
(1010) (eV) Be
5.61 (~10.0)
3.88 Mg
3.87
3.79 Zn
4.43
5.04 Cd
4.17
4.76 Ti
4.72
3.63 Zr
4.42
3.59 Hf
4.51 Sc
3.81
3.10 Y
3.60
3.08 -
… consistent with literature values
C. J. Fall et al., Journal of Physics: Condensed Matter 11, 2689 (1999)
T. Li et al., Phys. Rev. ST Accel. Beams 18, (2015)

4. UIC
Mg band structure Mg
(0001)-face emission
(1010)-face emission
S. Chatterjee & P. Sinha, J. Phys. F: Metal Phys. 5, 2089 (1975)

5. UIC Mg(0001) emission Isotropic bands in transverse plane
 ‘One-step’ DFT-based photoemission simulation
ħω = 4.75eV
(0001) = 3.87eV
Isotropic bands in transverse plane
 Radially symmetric emission; pT(1010) = pT(0110)
T. Li et al., Phys. Rev. ST Accel. Beams, 18 (2015)

6. UIC Mg(1010) emission Anisotropic bands in transverse plane
 ‘One-step’ DFT-based photoemission simulation
(ħω = 4.67eV)
(1010) = 3.66eV -
pT(0001)
pT(0110)
Mg(poly)
Anisotropic bands in transverse plane
 Asymetric emission: pT(0110) = 1.33pT(0001)
X.J. Wang et al., Proceedings of LINAC2002, Gyeongju, Korea.

7. UIC
(1010)-Face Emission Anisotropy Mg

8. UIC (1010)-Face Emission Anisotropy www.phys.ufl.edu/fermisurface/ MgBe

9. UIC (1010)-Face Emission Anisotropy www.phys.ufl.edu/fermisurface/ MgBe Y

10. UIC (1010)-Face Emission Anisotropy www.phys.ufl.edu/fermisurface/ MgBe Y Zr

11. UIC (1010)-Face Emission Anisotropy ; A = 0.577 = 1/3 Metal A(0001)Mg
Metal
A(0001)
A(0110)/A(0001) Be
0.160
2.10 Mg
0.241
1.33 Y
0.222
1.08 Hf
0.281 Sc
0.221
1.05 Ti
0.295
1.04 Zr
0.287
1.03 Be Y Zr
; A = = 1/3
T. Li et al., Phys. Rev. ST Accel. Beams, 18 (2015)

12. UIC
Summary
 DFT-based photoemission simulation of HCP metals
(0001)-face [basal plane] emission  Radially symmetric pT
(1010)-face emission  Asymmetric pT
Be Mg Y Hf Sc Ti Zr
More isotropic
Simulations consistent with poly-Mg measurement
 Predominantly (1010)-face emission 
pT(ħω < ) not evaluated: Expect
Robust surface state for Be(0001): eff  8.4eV, m*  1.5m0