Electronic structure calculations of an oxygen vacancy in KH2PO4

We present first-principles total-energy density-functional theory electronic structure calculations for the neutral and charge states of an oxygen vacancy in KH{sub 2}PO{sub 4} (KDP). Even though the overall DOS profiles for the defective KDP are quite similar to those of the perfect KDP, the oxygen vacancy in the neutral and +1 charge states induces defect states in the band gap. For the neutral oxygen vacancy, the gap states are occupied by two electrons. The difference between the integral of the total density of states (DOS) and the sum of the DOS projected on the atoms of 0.98 |e|, indicates that one of the two electrons resulting from the removal of the oxygen atom is trapped in the vacancy, while the other tends to delocalize in the neighboring atoms. For the +1 charge oxygen vacancy, the addition of the hole reduces the occupation of the filled gap-states in the neutral case from two to one electron and produces new empty states in the gap. The new empty gap states are very close to the highest occupied states, leading to a dramatic decrease of the band gap. The difference between the integral of the total DOS and the sum of the DOS projected on the atoms is 0.56 |e|, which implies that more than 56% of the redundant electron is trapped in the oxygen vacancy, and 44% spreads over the neighboring atoms. In sharp contrast, no defect states appear in the energy gap for the +2 charge O vacancy. Thus, the addition of the two holes completely compensates the two redundant electrons, and removes in turn the occupied gap states in the neutral case.

[1]  Stavros G. Demos,et al.  Ab initio study of the electronic and structural properties of the ferroelectric transition in KH2PO4 , 2001 .

[2]  Stavros G. Demos,et al.  Identification of electron and hole traps in KH2PO4 crystals , 2001 .

[3]  Stavros G. Demos,et al.  Investigation of optically active defect clusters in KH2PO4 under laser photoexcitation , 1999 .

[4]  D. Vanderbilt,et al.  Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. , 1990, Physical review. B, Condensed matter.

[5]  J. Carrasco,et al.  Theoretical study of bulk and surface oxygen and aluminum vacancies in α − Al 2 O 3 , 2004 .

[6]  N. P. Zaitseva,et al.  Identification of the intrinsic self-trapped hole center in KD2PO4 , 1999 .

[7]  R. Nelmes,et al.  The crystal structure of tetragonal KH2PO4and KD2PO4as a function of temperature , 1982 .

[8]  Shah,et al.  Population analysis of plane-wave electronic structure calculations of bulk materials. , 1996, Physical review. B, Condensed matter.

[9]  Mark A. Henesian,et al.  Ultraviolet-induced transient absorption in potassium dihydrogen phosphate and its influence on frequency conversion , 1994 .

[10]  J. Clemens,et al.  Paramagnetic and optical studies of radiation damage centers in K(H1−xDx)2PO4 , 1978 .

[11]  James W. Wells,et al.  ESR and ENDOR studies of irradiated potassium dihydrogen phosphate , 1986 .

[12]  W. E. Hughes,et al.  Electron Spin Resonance of Irradiated KH2PO4 and KD2PO4 , 1963 .

[13]  S. Demos,et al.  Electronic structure calculations of intrinsic and extrinsic hydrogen point defects in KH2PO4 , 2003 .

[14]  R. Abe,et al.  Electron Spin Resonance of γ-Irradiated KH 2 PO 4 , 1973 .

[15]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[16]  S G Demos,et al.  Wavelength dependence of laser-induced damage: determining the damage initiation mechanisms. , 2003, Physical review letters.

[17]  T. Arias,et al.  Iterative minimization techniques for ab initio total energy calculations: molecular dynamics and co , 1992 .

[18]  R. Nelmes.  STRUCTURAL STUDIES OF KDP AND THE KDP-TYPE TRANSITION BY NEUTRON AND X-RAY DIFFRACTION: 1970-1985 , 1987 .

[19]  Robert S. Hughes,et al.  Investigation of optically generated transient electronic defects and protonic transport in hydrogen-bonded molecular solids. Isomorphs of potassium dihydrogen phosphate , 1993 .

[20]  Stavros G. Demos,et al.  Raman scattering investigation of KH2PO4 subsequent to high fluence laser irradiation , 1998 .

[21]  Stavros G. Demos,et al.  Production and thermal decay of radiation-induced point defects in KD2PO4 crystals , 2003 .

[22]  Y. Ikuhara,et al.  First-principles calculations of intrinsic defects inAl2O3 , 2003 .

[23]  S G Demos,et al.  Electron- or hole-assisted reactions of H defects in hydrogen-bonded KDP. , 2003, Physical review letters.

[24]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[25]  Ming Yan,et al.  Hydrogen atoms in KH 2 PO 4 crystals , 1998 .

[26]  R. W. Godby,et al.  Supercell technique for total-energy calculations of finite charged and polar systems , 1997, cond-mat/9709234.

[27]  R. Abe,et al.  Anomaly of ESR Line Width in γ-Irradiated KH 2 PO 4 and KD 2 PO 4 , 1975 .