Supporting Information for Mid-infrared Nonlinear Optical ...
Supporting Information for Mid-infrared Nonlinear Optical Thiophosphates from LiZnPS4 to AgZnPS4: A Combined Experimental and Theoretical Study Molin Zhou,†, ‡, § Lei Kang,†, ‡, § Jiyong Yao,*, † Zheshuai Lin,*, † Yicheng Wu† and Chuangtian Chen† †
Beijing Center for Crystal R&D, Key Lab of Functional Crystals and Laser Technology of
Chinese Academy of Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China ‡
University of Chinese Academy of Sciences, Beijing 100190, PR China
§
These authors contributed equally.
*E-mail: [email protected] (J. Y. Y.) and [email protected] (Z. S. L.)
1. Syntheses of AgZnPS4 and LiZnPS4 2. Property characterization 3. Figure S1. Powder XRD patterns of AgZnPS4 and LiZnPS4 4. Figure S2. Polycrystalline powder morphology of AgZnPS4 5. Figure S3. Energy Dispersive Spectrometer (EDS) image of AgZnPS4 crystal 6. Computational methods 7. References
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1. Syntheses of AgZnPS4 and LiZnPS4 The following reagents were used as obtained: Li (Sinopharm Chemical Reagent Co., Ltd, 99%), S (Sinopharm Chemical Reagent Co., Ltd, 99.9%), Ag (Sinopharm Chemical Reagent Co., Ltd, 99.99%), ZnS (Aladdin Co., Ltd, 99.9%) and P2S5 (Sinopharm Chemical Reagent Co., Ltd, 99.9%). The binary starting material Li2S and Ag2S were prepared by the stoichiometric reaction of the elements in fused-silica tubes. The synthesis temperatures for Li2S and Ag2S are 573 K and 723 K, respectively. Traditional solid state reaction technique was applied to synthesize the polycrystalline samples of the title compounds. The mixture of Ag2S, ZnS, and P2S5 in the molar ratio of 1:2:1 and the mixture of Li2S, ZnS, and P2S5 in the molar ratio of 1:2:1 were ground and loaded, respectively, into fused-silica tubes under an Ar atmosphere in a glovebox. Then the tubes were sealed under 10−3 Pa and placed in a computer-controlled furnace. The samples were heated to 773 K and 673 K, respectively, for 10 h and were kept at the temperatures for 30 h, and, then, they were cooled to room temperature by switching off the furnace. The phase purity of the title compounds was confirmed by powder X–ray diffraction (XRD) collected at room temperature on a Bruker D8 Focus diffractometer with Cu Kα (λ= 1.5418 Å) radiation. The scanning step width of 0.05º and a fixed counting time 0.2 s/step were applied to record the patterns in the 2θ range of 10–70º. The measured XRD powder patterns match those simulated from reported single-crystal X–ray diffraction studies. The single crystals of AgZnPS4 were prepared by spontaneous crystallization method using pure single phase powder. Firstly, the powder was loaded into an vacuum-sealed quartz tube, then the tube was inserted into a furnace with the following procedure: heated to 973 K for 40 h and left at this temperature for about 50 h, then slowly cooled to 573 K at the rate of 3 K/h, finally rapidly cooled to room temperature. Block single crystals with yellow color were found in the tube. By means of EDS elemental analysis method, the chemical formula “AgZnPS4” was S2
confirmed. We also have tried to synthesize other analogues of LiZnPS4 (e.g., NaZnPS4, KZnPS4, CuZnPS4, AgCdPS4, etc.). Unfortunately, no analogues were obtained.
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2. Property Characterization UV-vis-NIR diffuse reflectance spectra The experimental spectra of AgZnPS4 and LiZnPS4 were measured by a Cary 5000 UV-vis-NIR spectrophotometer with a diffuse reflectance accessory over the range 300 nm (4.13 eV) to 1500 nm (0.83 eV). Thermal analysis A LabsysTM TG-DTA16 (SETARAM) thermal analyzer was used to investigate the thermal properties by the differential scanning calorimetric (DSC) analysis (the DSC was calibrated with Al2O3). Appropriate amouts of the title compounds samples were placed in a silica tube (5 mm o.d. × 3 mm i.d.) and subsequently sealed under a high vacuum. The heating and the cooling rates were both 15 K min-1. SHG measurements The optical SHG responses of AgZnPS4 and LiZnPS4 were measured by means of the Kurtz–Perry method.1 The fundamental light was the 2090 nm light generated with a Q-switched Ho: Tm: Cr: YAG laser. The particle size of the samples ranges from 20−320 µm for the measurement. The particle size of microcrystalline AgGaS2 in the range of 105−150 µm serves as a reference.
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3. Figure S1. Powder XRD patterns of AgZnPS4 and LiZnPS4.
Figure S1. Experimental (red) and simulated (black) powder X-ray diffraction data of AgZnPS4 (a) and LiZnPS4 (b). The differences in peak intensity for the same crystallographic index between the two patterns are believed to be caused by the preferential orientation of the powder samples.
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4. Figure S2. Polycrystalline powder morphology of AgZnPS4
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5. Figure S3. Energy Dispersive Spectrometer (EDS) image of AgZnPS4 crystal
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6. Computational methods The first-principles calculations are performed by the plane-wave pseudopotential method2 based on density functional theory (DFT)3 implemented in the CASTEP package4.
The
ion-electron
interactions
are
modeled
by
the
optimized
norm-conserving pseudopotentials5 for all constituent elements. A kinetic energy cutoff of 800 eV is chosen with Monkhorst-Pack k-point6 meshes spanning less than 0.04 per Å3 in the Brillouin zone. Based on the electronic band structure, the imaginary part of the dielectric function is calculated and the real part of the dielectric function is determined using the Kramers–Kronig transform, from which the refractive indices n (and the birefringence ∆n) are obtained. Furthermore, The second order susceptibility χ(2) and the second-harmonic generation (SHG) coefficients dij are calculated using an expression originally proposed by Rashkeev et al.7 and developed by Lin et al.8. The second-order susceptibility χijk is represented as: χ
ijk
=χ
ijk
(VE) + χ
ijk
(VH) + χ
ijk
(twobands)
where χijk (VE) and χijk (VH) denote the contributions from virtual-electron processes and virtual-hole processes, respectively, and χijk (two bands) gives the contribution from two band processes to χ(2). The formulas for calculating χijk (VE),
χijk (VH) and χijk (two bands) are as following: v 1 e3 d 3k 2 χ (VE) = 2 3 ∑ ∫ 3 P(ijk ) Im[ pvci pccj ' pck' v ] 3 2 + 4 ijk 2h m vcc ' 4π ωcvωvc ' ωvcωc ' v v 1 e3 d 3k 2 χ (VH) = 2 3 ∑ ∫ 3 P(ijk ) Im[ pvvi ' pvj' c pcvk ] 3 2 + 4 ijk 2h m vv ' c 4π ωcvωv ' c ωvcωcv ' v Im[ pvci pcvj ( pvvk − pcck )] e3 d 3k χ (twobands) = 2 3 ∑ ∫ 3 P(ijk ) ijk h m vc 4π ωvc5
Here, i, j and k are Cartesian components, v and v’ denote VB, and c and c’ denote CB. P(ijk) denotes full permutation. It should be emphasized that the refractive indices and SHG coefficients can be accurately obtained by DFT in principle because these optical properties are determined by the virtual electronic excited processes which are described by the first- and second-order perturbations, respectively, on the ground state wavefunctions. S8
7. References (1) Kurtz, S. K.; Perry, T. T. J.Appl. Phys. 1968, 39, 3798. (2) Payne, M. C.; Teter, M. P.; Allan, D. C.; Arias, T. A.; Joannopoulos, J. D. Rev. Mod. Phys. 1992, 64, 1045-1097. (3) Kohn, W. Rev. Mod. Phys. 1999, 71, 1253-1266. (4) Clark, S. J.; Segall, M. D.; Pickard, C. J.; Hasnip, P. J.; Probert, M. J.; Refson, K.; Payne, M. C. Z. Kristallogr. 2005, 220, 567-570. (5) Rappe, A. M.; Rabe, K. M.; Kaxiras, E.; Joannopoulos, J. D. Phys. Rev. B 1990, 41, 1227-1230. (6) Monkhorst, H. J.; Pack, J. D. Phys. Rev. B 1976, 13, 5188-5192. (7) Rashkeev, S. N.; Lambrecht, W. R. L.; Segall, B. Phys. Rev. B 1998, 57, 3905-3919. (8) Lin, J.; Lee, M. H.; Liu, Z. P.; Chen, C. T.; Pickard, C. J. Phys. Rev. B 1999, 60, 13380-13389.
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Beijing Center for Crystal R&D, Key Lab of Functional Crystals and Laser Technology of
Chinese Academy of Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China ‡
University of Chinese Academy of Sciences, Beijing 100190, PR China
§
These authors contributed equally.
*E-mail: [email protected] (J. Y. Y.) and [email protected] (Z. S. L.)
1. Syntheses of AgZnPS4 and LiZnPS4 2. Property characterization 3. Figure S1. Powder XRD patterns of AgZnPS4 and LiZnPS4 4. Figure S2. Polycrystalline powder morphology of AgZnPS4 5. Figure S3. Energy Dispersive Spectrometer (EDS) image of AgZnPS4 crystal 6. Computational methods 7. References
S1
1. Syntheses of AgZnPS4 and LiZnPS4 The following reagents were used as obtained: Li (Sinopharm Chemical Reagent Co., Ltd, 99%), S (Sinopharm Chemical Reagent Co., Ltd, 99.9%), Ag (Sinopharm Chemical Reagent Co., Ltd, 99.99%), ZnS (Aladdin Co., Ltd, 99.9%) and P2S5 (Sinopharm Chemical Reagent Co., Ltd, 99.9%). The binary starting material Li2S and Ag2S were prepared by the stoichiometric reaction of the elements in fused-silica tubes. The synthesis temperatures for Li2S and Ag2S are 573 K and 723 K, respectively. Traditional solid state reaction technique was applied to synthesize the polycrystalline samples of the title compounds. The mixture of Ag2S, ZnS, and P2S5 in the molar ratio of 1:2:1 and the mixture of Li2S, ZnS, and P2S5 in the molar ratio of 1:2:1 were ground and loaded, respectively, into fused-silica tubes under an Ar atmosphere in a glovebox. Then the tubes were sealed under 10−3 Pa and placed in a computer-controlled furnace. The samples were heated to 773 K and 673 K, respectively, for 10 h and were kept at the temperatures for 30 h, and, then, they were cooled to room temperature by switching off the furnace. The phase purity of the title compounds was confirmed by powder X–ray diffraction (XRD) collected at room temperature on a Bruker D8 Focus diffractometer with Cu Kα (λ= 1.5418 Å) radiation. The scanning step width of 0.05º and a fixed counting time 0.2 s/step were applied to record the patterns in the 2θ range of 10–70º. The measured XRD powder patterns match those simulated from reported single-crystal X–ray diffraction studies. The single crystals of AgZnPS4 were prepared by spontaneous crystallization method using pure single phase powder. Firstly, the powder was loaded into an vacuum-sealed quartz tube, then the tube was inserted into a furnace with the following procedure: heated to 973 K for 40 h and left at this temperature for about 50 h, then slowly cooled to 573 K at the rate of 3 K/h, finally rapidly cooled to room temperature. Block single crystals with yellow color were found in the tube. By means of EDS elemental analysis method, the chemical formula “AgZnPS4” was S2
confirmed. We also have tried to synthesize other analogues of LiZnPS4 (e.g., NaZnPS4, KZnPS4, CuZnPS4, AgCdPS4, etc.). Unfortunately, no analogues were obtained.
S3
2. Property Characterization UV-vis-NIR diffuse reflectance spectra The experimental spectra of AgZnPS4 and LiZnPS4 were measured by a Cary 5000 UV-vis-NIR spectrophotometer with a diffuse reflectance accessory over the range 300 nm (4.13 eV) to 1500 nm (0.83 eV). Thermal analysis A LabsysTM TG-DTA16 (SETARAM) thermal analyzer was used to investigate the thermal properties by the differential scanning calorimetric (DSC) analysis (the DSC was calibrated with Al2O3). Appropriate amouts of the title compounds samples were placed in a silica tube (5 mm o.d. × 3 mm i.d.) and subsequently sealed under a high vacuum. The heating and the cooling rates were both 15 K min-1. SHG measurements The optical SHG responses of AgZnPS4 and LiZnPS4 were measured by means of the Kurtz–Perry method.1 The fundamental light was the 2090 nm light generated with a Q-switched Ho: Tm: Cr: YAG laser. The particle size of the samples ranges from 20−320 µm for the measurement. The particle size of microcrystalline AgGaS2 in the range of 105−150 µm serves as a reference.
S4
3. Figure S1. Powder XRD patterns of AgZnPS4 and LiZnPS4.
Figure S1. Experimental (red) and simulated (black) powder X-ray diffraction data of AgZnPS4 (a) and LiZnPS4 (b). The differences in peak intensity for the same crystallographic index between the two patterns are believed to be caused by the preferential orientation of the powder samples.
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4. Figure S2. Polycrystalline powder morphology of AgZnPS4
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5. Figure S3. Energy Dispersive Spectrometer (EDS) image of AgZnPS4 crystal
S7
6. Computational methods The first-principles calculations are performed by the plane-wave pseudopotential method2 based on density functional theory (DFT)3 implemented in the CASTEP package4.
The
ion-electron
interactions
are
modeled
by
the
optimized
norm-conserving pseudopotentials5 for all constituent elements. A kinetic energy cutoff of 800 eV is chosen with Monkhorst-Pack k-point6 meshes spanning less than 0.04 per Å3 in the Brillouin zone. Based on the electronic band structure, the imaginary part of the dielectric function is calculated and the real part of the dielectric function is determined using the Kramers–Kronig transform, from which the refractive indices n (and the birefringence ∆n) are obtained. Furthermore, The second order susceptibility χ(2) and the second-harmonic generation (SHG) coefficients dij are calculated using an expression originally proposed by Rashkeev et al.7 and developed by Lin et al.8. The second-order susceptibility χijk is represented as: χ
ijk
=χ
ijk
(VE) + χ
ijk
(VH) + χ
ijk
(twobands)
where χijk (VE) and χijk (VH) denote the contributions from virtual-electron processes and virtual-hole processes, respectively, and χijk (two bands) gives the contribution from two band processes to χ(2). The formulas for calculating χijk (VE),
χijk (VH) and χijk (two bands) are as following: v 1 e3 d 3k 2 χ (VE) = 2 3 ∑ ∫ 3 P(ijk ) Im[ pvci pccj ' pck' v ] 3 2 + 4 ijk 2h m vcc ' 4π ωcvωvc ' ωvcωc ' v v 1 e3 d 3k 2 χ (VH) = 2 3 ∑ ∫ 3 P(ijk ) Im[ pvvi ' pvj' c pcvk ] 3 2 + 4 ijk 2h m vv ' c 4π ωcvωv ' c ωvcωcv ' v Im[ pvci pcvj ( pvvk − pcck )] e3 d 3k χ (twobands) = 2 3 ∑ ∫ 3 P(ijk ) ijk h m vc 4π ωvc5
Here, i, j and k are Cartesian components, v and v’ denote VB, and c and c’ denote CB. P(ijk) denotes full permutation. It should be emphasized that the refractive indices and SHG coefficients can be accurately obtained by DFT in principle because these optical properties are determined by the virtual electronic excited processes which are described by the first- and second-order perturbations, respectively, on the ground state wavefunctions. S8
7. References (1) Kurtz, S. K.; Perry, T. T. J.Appl. Phys. 1968, 39, 3798. (2) Payne, M. C.; Teter, M. P.; Allan, D. C.; Arias, T. A.; Joannopoulos, J. D. Rev. Mod. Phys. 1992, 64, 1045-1097. (3) Kohn, W. Rev. Mod. Phys. 1999, 71, 1253-1266. (4) Clark, S. J.; Segall, M. D.; Pickard, C. J.; Hasnip, P. J.; Probert, M. J.; Refson, K.; Payne, M. C. Z. Kristallogr. 2005, 220, 567-570. (5) Rappe, A. M.; Rabe, K. M.; Kaxiras, E.; Joannopoulos, J. D. Phys. Rev. B 1990, 41, 1227-1230. (6) Monkhorst, H. J.; Pack, J. D. Phys. Rev. B 1976, 13, 5188-5192. (7) Rashkeev, S. N.; Lambrecht, W. R. L.; Segall, B. Phys. Rev. B 1998, 57, 3905-3919. (8) Lin, J.; Lee, M. H.; Liu, Z. P.; Chen, C. T.; Pickard, C. J. Phys. Rev. B 1999, 60, 13380-13389.
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