Stability and electronic structure of hydrogen vacancies in ADP: hybrid DFT with vdW correction

Progress on deuterated potassium dihydrogen phosphate (DKDP) crystals for high power laser system application

In this review, we introduce the progress in the growth of large-aperture DKDP crystals and some aspects of crystal quality including determination of deuterium content, homogeneity of deuterium distribution, residual strains, nonlinear absorption, and laser-induced damage resistance for its application in high power laser system. Large-aperture high-quality DKDP crystal with deuteration level of 70% has been successfully grown by the traditional method, which can fabricate the large single-crystal optics with the size exceeding 400 mm. Neutron diffraction technique is an efficient method to research the deuterium content and 3D residual strains in single crystals. More efforts have been paid in the processes of purity of raw materials, continuous filtration technology, thermal annealing and laser conditioning for increasing the laser-induced damage threshold (LIDT) and these processes enable the currently grown crystals to meet the specifications of the laser system for inertial confinement fusion (ICF), although the laser damage mechanism and laser conditioning mechanism are still not well understood. The advancements on growth of large-aperture high-quality DKDP crystal would support the development of ICF in China.

Hybrid density functional theory for the stability and electronic properties of Fe-doped cluster defects in KDP crystal

The defect state induced by FeP2− + VO2+ cluster defects strengthens the charge transfer along the direction of x in KDP crystal.

First-principles studies on optical absorption of [010] screw dislocation in KDP crystals

The stress caused by the [010] dislocation in KDP deforms the crystal structure, introduces extra optical absorption and narrows the band gap.

Structural stress and extra optical absorption induced by the intrinsic cation defects in KDP and ADP crystals: a theoretical study

V_P⁵⁻ defects are regarded as one of the main sources for the initial structural breakdown in KDP compared with ADP.

Structural engineering of bilayer PtSe2 thin films: a first-principles study

PtSe₂ is an emerging layered two-dimensional material of applied interest. Its monolayer shows promising properties for applications in electronic devices, while the bandgap of a multilayer PtSe₂ film can be tuned via changing its thickness. In this work the bilayer PtSe₂ thin films are investigated as an example of structural engineering with first-principles calculations. Various van der Waals corrections schemes are firstly discussed, and the optB86b scheme shows a better description of the semiconductor-metal transition for PtSe₂ films. Six bilayer PtSe₂ thin films in different stacking modes are constructed in order to structurally tune the electronic and transport properties. The bandgap can be effectively broadened with the structural engineering for wider potential applications. The carrier mobility, dynamical stability and Raman spectra are also calculated and discussed.

Comparison of hydrogen vacancies in KDP and ADP crystals: a combination of density functional theory calculations and experiment

The hydrogen vacancy (VH) is the most common point defect that may lead to optical damage of potassium dihydrogen phosphate (KDP) and its analog ammonium dihydrogen phosphate (ADP), further limiting their practical application in high-power laser systems. In this work, we have grown KDP and ADP crystals by using a rapid growth method, and investigated the physical origin of the different stability of VH as well as the defect-induced electronic structure and optical absorption in KDP and ADP crystals. The inclusion of van der Waals correction to density functional theory calculations is found to have little influence on VH energetics of KDP whereas it largely reduces the charge transition level ε(+/-) of VH by >2 eV in ADP. It is found that hydrogen vacancies mainly contribute to the redshift of the measured absorption edges of both KDP and ADP crystals. Owing to the varied lattice environments and locations, the VH defects exhibit different stability, and electronic and optical properties in KDP and ADP crystals. Notably, the extra optical absorption caused by the positively-charged VH in KDP could be largely reduced by decreasing the defect concentration, whereas ADP exhibits defect-location dependence - the optical damage center of the VH in the NH4+ group could not be eliminated because of electron capture of its neighboring N atoms. The calculation results help us to better understand the origin of laser damage in KDP and ADP crystals.