CsSiB3O7: A Beryllium-Free Deep-Ultraviolet Nonlinear Optical

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CsSiB3O7: A Beryllium-Free Deep-Ultraviolet Nonlinear Optical Material Discovered by the Combination of Electron Diffraction and First-Principles Calculations Zhengyang Zhou,†,‡,# Yi Qiu,‡,# Fei Liang,§,# Lukás ̌ Palatinus,∥ Morgane Poupon,∥ Tao Yang,† Rihong Cong,† Zheshuai Lin,*,§ and Junliang Sun*,‡ †

College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, People’s Republic of China College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People’s Republic of China § 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, People’s Republic of China ∥ Institute of Physics of the CAS, v.v.i., Na Slovance 2, 182 21 Prague, Czech Republic ‡

S Supporting Information *

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detection of light atoms by above established 3D ED techniques difficult. In this study, dynamical refinements of precession electron diffraction tomography (PEDT), by which even the position of hydrogen atoms can be determined,31−33 was employed to explore the new deep-UV NLO materials in the Cs−Si−B−O system. Because it is well agreed that the excitation energies of AOx (A = alkali metal), SiO4, BO4 and BO3 are near the deepUV region, and the large microscopic doubling frequency coefficient possessed by the π-conjugated BO3 makes alkali metal borosilicates promising candidates for deep-UV NLO materials.34 So far, Cs2SiB4O9 is the only alkali metal borosilicate with deep-UV NLO property.35 Herein, the application of the PEDT technique led to the discovery of a new material CsSiB3O7, which was originally a minor impurity in a multicomponent powder sample. Its structure was determined by dynamical refinements of PEDT data, and is in fact isostructural with the NLO material CsGeB3O7. The effects of the replacement of Ge by Si are interesting. First, CsSiB3O7 possesses a severe structural stress due to the smaller SiO4 compared with GeO4, which are four-connected nodes of the anionic framework, and second, the Si to Ge replacement leads to a calculated 7.45 eV direct band gap, corresponding to a theoretical cutoff edge at 166 nm, which means CsSiB3O7 is supposed to be the promising deep-UV NLO material. At the beginning, six random compositions in the boron-rich region of Cs−Si−B−O system were selected (Table S1), and polycrystalline samples were prepared by typical high temperature solid state reaction. Other than two known compounds, Cs2SiB4O9 and CsSi2BO6,36 there are some small unidentified peaks in PXRD data for one of the six samples (Figure S1). The first idea is to check the possible isomorphism to other alkali metal borogermanates (Figure S2), such as CsGeB3O7, Rb4Ge3B6O17 and K2Ge3B2O10.37,38 However, there is no clear correlation between them, suggesting a new borosilicate was obtained as an impurity in our study.

eep-ultraviolet (deep-UV) nonlinear optical (NLO) materials are of great academic and technological interest due to their capability to produce coherent light of wavelengths below 200 nm, which have important applications in laser science and technology, such as photolithography, semiconductor manufacturing, laser micromatching, super highresolution spectroscopy, and laser cooling.1−4 After continuous efforts over several decades, KBe2BO3F2 (KBBF), LiB3O5 (LBO), YAl 3 (BO 3 ) 4 , CsB 3 O 5 , K 2 Al 2 B 2 O 7 (KABO), βKBe2B3O7, KSrCO3F, etc. with deep-UV or near UV absorption edges have been discovered;5−14 however, KBBF is the only material that can practically generate deep-UV coherent light at 177 nm by the direct second harmonic generation (SHG) process. The major problems of KBBF are the use of highly toxic BeO and the serious layering tendency of single crystal growth. Therefore, it is desirable to discover new beryllium-free deep-UV NLO materials with absorption edges below 177 nm, along with satisfied NLO property and chemical stability. Rational modifications to KBBF by ionic replacements or synthesizing analogues to other known NLO materials are the main strategies currently, and indeed a number of new NLO materials with promising properties are discovered, such as K 3 Ba 3 Li 2 Al 4 B 6 O 20 F, Na 2 CsBe 6 B 5 O 15 , β-Rb 2 Al 2 B 2 O 7 and AB4O6F (A = NH4, Cs).15−19 In general, it is time-consuming and sometimes very difficult to figure out the proper conditions for single crystal growth or pure phase synthesis for structure determination and property measurements when discovering the new materials. Alternatively, electron microscopy (EM) is a preferring option to accelerate the discovery of new materials, possessing the superiority on determining submicron crystal structures from impure samples. For instance, once detecting an unknown phase, energy dispersive X-ray spectroscopy (EDS) may offer an approximate composition, and established 3D electron diffraction (ED) techniques, such as ADT, RED, PEDT, microED and IEDT, could be applied to solve the crystal structure roughly,20−26 in the following, Rietveld refinements upon powder X-ray diffraction (PXRD) data would give the fine structure.27−30 Unfortunately, deep-UV NLO materials usually contain both the heavy atoms (i.e., Rb, Cs, Ba, Sr) and the light atoms (i.e., B, C), which makes the © 2018 American Chemical Society

Received: February 5, 2018 Revised: March 26, 2018 Published: March 26, 2018 2203

DOI: 10.1021/acs.chemmater.8b00545 Chem. Mater. 2018, 30, 2203−2207

Communication

Chemistry of Materials After careful checking, a full set of PEDT data of this new phase was collected on a small submicron particle under TEM. An overview of the PEDT data is shown in Figure 1a. An

Figure 2. (a) Structure of CsSiB3O7 project along the c-axis. (d) Structure of CsSiB3O7 project along the a-axis. There are 2 × 2 × 2 unit cells (0-2a, 0-2b, 0-2c) in the figure. Cs, purple balls; Si, yellow balls; O, red balls; B, incarnadine balls.

Table S5), proving the correctness of the determined structure. As mentioned, our first screen on the PXRD failed to identify the isomorphism between CsSiB3O7 and the known phase CsGeB3O7 (Figure S3), because the cell parameters of CsSiB3O7 exhibit an anisotropic expansion/contraction along the b-axis/ac-plane, compared to CsGeB3O7 (i.e., CsSiB3O7: a = 9.2171(6) Å, b = 10.0271(18) Å, and c = 6.9348(2) Å, CsGeB3O7: a = 9.542(3) Å, b = 9.823(3) Å, and c = 7.009(2) Å). This anisotropic unit cell change could be due to the difference between the T−O−B angles. As shown in Figure 2, the Si−O−B angles in CsSiB3O7 (126.0(5), 126.9(7), 131.9(7), and 141.9(5)°) are generally larger than the corresponding Ge−O−B angles in CsGeB3O7 (120.67(18), 121.80(17), 125.6(2), and 137.3(2)°).37 This difference is also similar to that in zeolitic strutures due to the shorter Si−O bond length. To confirm the correctness of the structure determined by dynamical refinement of PEDT data, the Rietveld refinement of PXRD data of pure polycrystalline sample synthesized according to the composition CsSiB3O7 was performed (Figure S4). The greatest difference between the atomic coordinates determined by dynamical refinement of PEDT data and by Rietveld refinement of PXRD data is that the x coordinates of B3 are 0.3192(6) and 0.306(2) respectively, which is about 0.12 Å and confirmed the correctness of the model obtained from PEDT data. The details of Rietveld refinement of PXRD are provided in Table S6. The atomic parameters of CsSiB3O7 determined by Rietveld refinement of PXRD are given in Table S7. As CsSiB3O7 crystallizes in the noncentrosymmetric space group Pna21, its powder SHG intensity was estimated by the Kurtz−Perry method42 with incident laser at 1064 nm. As shown in Figure 3a, CsSiB3O7 is type-I phase matchable, and its

Figure 1. (a) The 3D view of the diffraction data and the submicrocrystal used to collect the PEDT data. (b−d) The hk0, h0l, and 0kl plane diffraction patterns, respectively, reconstructed from the 3D PEDT data. Because of the dynamical effects, some weak reflections violate the reflection conditions.

orthorhombic unit cell of a = 9.2171(6) Å, b = 10.0271(18) Å, and c = 6.9348(2) Å can index the whole data set as shown in Figures 1b−d. Although a fraction of the reciprocal space was missing in the PEDT data, the real missing part is smaller than what appears and the final data completeness is 86% due to the relatively high symmetry (orthorhombic) The reflection conditions are h0l, h = 2n, 0kl, k + l = 2n, indicating the possible space group Pnam or Pna21. Ab initio structure solution was performed by the Charge Flipping algorithm using the program Superflip.39 All Cs, Si, O and B atoms were located according to the combination of kinematical approximation structure solution and the common geometries of BO3, BO4, and SiO4 with the polar space group Pna21. Because of the complicated relations between structure factors and diffraction intensities introduced by dynamical effect, kinematical refinement cannot be used to determine the correctness of such a build structure. Then the dynamical refinement of the PEDT data yields the determined structure with the formula of CsSiB3O7. The as-obtained crystallographic data and refinement details are provided in Table S2. The atomic parameters of CsSiB3O7 are given in Tables S3. In CsSiB3O7, one tetrahedral BO4 (B1O4) and two triangular BO3 (B2O3 and B3O3) are connected into the typical anionic groups B3O7 through corner-sharing. The Si is tetrahedrally coordinated by four O atoms from four B3O7 anionic groups. Such an alternative connection of SiO4 and B3O7 anionic groups results in a three-dimensional B−O−Si anionic network with two types of 1D helical tunnels along the c-axis (Figure 2a) and one type of 1D tunnels along the a-axis (Figure 2b). All the Cs+ cations are located in the tunnels to compensate the negative charges from the borosilicate framework, and coordinated by 12 O atoms with the distances from 3.017(6) to 3.837(6) Å. The detailed bond lengths and angles are listed in Table S4. The bond valence sums (BVS) calculations40,41 of Cs, Si, B, and O are all consistent with the expected values (see

Figure 3. (a) SHG intensity as a function of particle size for CsSiB3O7. KDP serves as the reference. The curve is drawn as a guide to the eye and not a fit to the data. (b) UV/vis diffuse reflectance spectrum curve of CsSiB3O7. 2204

DOI: 10.1021/acs.chemmater.8b00545 Chem. Mater. 2018, 30, 2203−2207

Communication

Chemistry of Materials SHG efficiency is about 0.8 × KH2PO4 (KDP) at the particle sizes of 168−262 μm, which is a little larger than those of KABO (0.7 × KDP)9 and β-KBe2B3O7 (0.68 × KDP)10 and smaller than that of CsGeB3O7 (1.5 × KDP).37 Most importantly, the UV/vis diffuse reflectance spectrum for the polycrystalline CsSiB3O7 shows a high transparency even at deep UV-range (see Figure 3b), i.e., >70% from 300 to 1200 nm and nearly 65% at 200 nm, which suggested the cutoff edge is below 200 nm. Because of the incongruent melting property of CsSiB3O7 (Figure S5), the exploration of conditions to grow a millimeter sized single crystal will take a very long time. To gain deep insights into the band structure and optical properties, the firstprinciples calculations43 were performed on CsSiB3O7 as well as its analogue CsGeB3O7 for comparison. The scissor-operator44 corrected electronic band structures of CsSiB3O7 (Figure 4a)

which is slightly smaller than that of LBO (∼0.04), the relatively large range of Δn to achieve the phase-matching condition through SFG process is still expected to allow the application of CsSiB3O7 in coherent vacuum ultraviolet radiation. Under the restriction of Kleinman’s symmetry, CsSiB3O7 has three nonzero independent SHG coefficients (d15 = 0.17 pm/V, d24 = 0.45 pm/V, and d33 = −0.55 pm/V), which are consistent in the experimental results and comparable with KBBF (0.47 pm/V) and KABO (0.45 pm/V). In comparison, the corresponding calculated SHG coefficients of CsGeB3O7 are +0.25, +0.57, −0.71 pm/V (Table S8), which is slightly higher than those of title compound. In our opinion, the enhanced SHG effect in CsGeB3O7 can be attributed to two aspects: (i) Narrowed forbidden energy gap. As we all know, an increase of Eg would result in the decrease of dij in Rashkeev’s second-order susceptibility χ(2) formula.48 Compared wi th CsSiB3O7, the bandgap of CsGeB3O7 decrease by 1.8 eV, thus it exhibits stronger nonlinear response. (ii) the enhanced contribution of GeO4 tetrahedra. The results from real-space atom-cutting technique49 (Tables 1 and S8) demonstrate that the total Table 1. Real-Space Atom-Cutting Analysis

Figure 4. (a) Band structures of CsSiB3O7. (b) Total and partial DOS curves of CsSiB3O7. The Ef is displayed as a dashed vertical line and was used as a reference for all energy values (0 eV).

dij

CsSiB3O7a

Cs+

(SiO4)4−

(B3O7)5−

d15 (pm/V) d24 (pm/V) d33 (pm/V)

0.17 0.45 −0.55

0.01 0.05 −0.07

0.09 0.16 −0.17

0.12 0.38 −0.35

a

Because of the corner-sharing O atoms between (SiO4)4− and (B3O7)5−, the dij parameters of CsSiB3O7 are not equal to the total of dij parameters of Cs+, (SiO4)4−, and (B3O7)5−.

and CsGeB3O7 (Figure S6a) along the lines of high symmetry points in the first Brillouin zone show that CsSiB3O7 and CsGeB3O7 both possess the direct band gap with the energy of 7.45 and 5.67 eV, respectively. The density of states (DOS) and partial DOS projected on the constitutional atoms in CsSiB3O7 (Figure 4b) indicate that the valence band (VB) maximum is exclusively occupied by O 2p orbitals, meanwhile the CB bottom is contributed from the orbitals of all constituent atoms. Because the optical effects of a crystal mainly originate from the optical transition between the electronic states close to the band gap,45,46 it is anticipated that they are dominantly contributed from the groups constructed by Si, B, and O, whereas the contribution from the orbitals of the Cs+ cations is negligibly small. Compared with CsGeB3O7 (Figure S6b), the difference of s and p states between Ge and Si influences the CB bottom significantly, for example, the high contribution of the Ge s states leads to a much lower potential of the CB bottom. This is the reason why CsSiB3O7 has a much wider band gap compared to CsGeB3O7. In the literature, CsGeB3O7 was reported to have the UV cutoff wavelength at 215 nm,37 and here the calculated band gap of CsSiB3O7 is as high as 7.45 eV, corresponding to a theoretical cutoff edge at 166 nm. This is one of the necessary prerequisites for a NLO crystal to generate coherent light at 177 nm, a laser that is crucial to a range of advanced scientific instruments through possible frequency mixing. In addition, such a wide gap of 7.45 eV is also beneficial to have a high laser damage threshold. To achieve noticeable deep-UV coherent light output, an NLO crystal must have a proper birefringence Δn to achieve the phase-matching condition. In previous work, LBO crystal has been used in coherent vacuum ultraviolet radiation ranged from 187 to 195 nm through sum frequency generation (SFG) process.47 Although the calculated Δn of CsSiB3O7 is 0.035,

contribution of B3O7 and SiO4 (GeO4) groups to the SHG coefficients is more than 80%, whereas the contribution of Cs+ is relatively small (∼10%). Notably, the GeO4 groups make 30% larger contribution to total SHG coefficients than those of SiO4 groups, owing to their more distorted tetrahedral configuration and flexible dipole electrons. Moreover, to identify the spatial distribution of the electronic states dominating the SHG response, the visual SHG densities of occupied states are displayed in Figure 5. Clearly, O 2p

Figure 5. SHG-weighted charge density map of CsB3SiO7, (a,b)B3O7 groups and (c,d) SiO4 groups. Si, yellow balls; O, red balls; B, incarnadine balls. 2205

DOI: 10.1021/acs.chemmater.8b00545 Chem. Mater. 2018, 30, 2203−2207

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electrons are the dominant contributor to the SHG coefficient in occupied states. In particular, it is also found that the coplanar O in BO3 dimers plays a much more important role in SHG effects because of their parallel p orbitals. According to the anion group theory, the π-conjugated electron anionic groups, such as NO3, CO3 and BO3, have the enhanced secondorder susceptibility over those without the π-conjugated systems.34 So, it is anticipated that there is smaller contribution from the 4-fold coordination BO4 than those of planar BO3. Additionally, SiO4 groups also make non-negligible contributions to SHG owing to their strong orbital hybridization and electron transfer. Combined with atom-cutting results, the contribution of SiO4 to d15, d24 and d33 are 40%, 35% and 35%, respectively. These results illustrate that tetrahedral units SiO4 is also good molecular construction blocks to obtain large SHG effect in deep-UV NLO crystals. Without the need of single crystal growth, a new borosilicate CsSiB3O7 was discovered by dynamical refinements of PEDT data, and the interesting point is the remarkably high transparency at deep UV-light range and even likely applicable to generate coherent light below 200 nm according to the firstprinciples calculations. Particularly, the timely input from firstprinciples calculations accelerate the identification of promising NLO materials before large single crystals could be prepared. Our achievement in the case of CsSiB3O7 represents a successful strategy of developing new NLO materials, which is also applicable for other types of functional materials.

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REFERENCES

(1) Savage, N. Ultraviolet lasers. Nat. Photonics 2007, 1, 83−85. (2) Cyranoski, D. Materials science: China’s crystal cache. Nature 2009, 457, 953−955. (3) Liu, G.; Wang, G.; Zhu, Y.; Zhang, H.; Zhang, G.; Wang, X.; Zhou, Y.; Zhang, W.; Liu, H.; Zhao, L.; Meng, J.; Dong, X.; Chen, C.; Xu, Z.; Zhou, X. Development of a vacuum ultraviolet laser-based angle-resolved photoemission system with a super high energy resolution better than 1meV. Rev. Sci. Instrum. 2008, 79, 023105. (4) Tran, T. T.; Yu, H.; Rondinelli, J. M.; Poeppelmeier, K. R.; Halasyamani, P. S. Deep Ultraviolet Nonlinear Optical Materials. Chem. Mater. 2016, 28, 5238−5258. (5) Togashi, T.; Kanai, T.; Sekikawa, T.; Watanabe, S.; Chen, C.; Zhang, C.; Xu, Z.; Wang, J. Generation of vacuum-ultraviolet light below 160 nm in a KBBF crystal by the fifth harmonic of a singlemode Ti: sapphire laser. Opt. Lett. 2003, 28, 254−256. (6) Chen, C.; Wu, Y.; Jiang, A. D.; Wu, B.; You, G.; Li, R.; Lin, S. New nonlinear-optical crystal: LiB3O5. J. Opt. Soc. Am. B 1989, 6, 616−621. (7) Rytz, D.; Gross, A.; Vernay, S.; WEsemann, V. YAl3(BO3)4: a novel NLO crystal for frequency conversion to UV wavelengths. Proc. SPIE 2008, 6998, 699814. (8) Wu, Y.; Sasaki, T.; Nakai, N.; Yokotani, A.; Tang, H.; Chen, C. CsB3O5: A new nonlinear optical crystal. Appl. Phys. Lett. 1993, 62, 2614−2615. (9) Ye, N.; Zeng, W.; Jiang, J.; Wu, B.; Chen, C.; Feng, B.; Zhang, X. New nonlinear optical crystal K2Al2B2O7. J. Opt. Soc. Am. B 2000, 17, 764−768. (10) Wang, S.; Ye, N.; Li, W.; Zhao, D. Alkaline Beryllium Borate NaBeB3O6 and ABe2B3O7 (A = K, Rb) as UV Nonlinear Optical Crystals. J. Am. Chem. Soc. 2010, 132, 8779−8786. (11) Zou, G.; Ye, N.; Huang, H.; Lin, X. Alkaline-alkaline earth fluoride carbonate crystals ABCO3F (A = K, Rb, Cs; B = Ca, Sr, Ba) as nonlinear optical materials. J. Am. Chem. Soc. 2011, 133, 20001− 20007. (12) Tran, T. T.; Young, J.; Rondinelli, J. M.; Halasyamani, P. S. Mixed-Metal Carbonate Fluorides as Deep-Ultraviolet Nonlinear Optical Materials. J. Am. Chem. Soc. 2017, 139, 1285−1295. (13) Wu, H.; Yu, H.; Pan, S.; Halasyamani, P. S. Deep-Ultraviolet Nonlinear-Optical Material K3Sr3Li2Al4B6O20F: Addressing the Structural Instability Problem in KBe2BO3F2. Inorg. Chem. 2017, 56, 8755− 8758. (14) Yu, H.; Young, J.; Wu, H.; Zhang, W.; Rondinelli, J. M.; Halasyamani, P. S. The Next-Generation of Nonlinear Optical Materials: Rb3Ba3Li2Al4B6O20F-Synthesis, Characterization, and Crystal Growth. Adv. Opt. Mater. 2017, 5, 1700840. (15) Zhao, S.; Kang, L.; Shen, Y.; Wang, X.; Asghar, M. A.; Lin, Z.; Xu, Y.; Zeng, S.; Hong, M.; Luo, J. Designing a Beryllium-Free DeepUltraviolet Nonlinear Optical Material without a Structural Instability Problem. J. Am. Chem. Soc. 2016, 138, 2961−2964. (16) Wang, S.; Ye, N. Na2CsBe6B5O15: An Alkaline Beryllium Borate as a Deep-UV Nonlinear Optical Crystal. J. Am. Chem. Soc. 2011, 133, 11458−11461. (17) Tran, T. T.; Koocher, N. Z.; Rondinelli, J. M.; Halasyamani, P. S. Beryllium-Free β-Rb2Al2B2O7 as a Possible Deep-Ultraviolet Nonlinear Optical Material Replacement for KBe2BO3F2. Angew. Chem., Int. Ed. 2017, 56, 1−6. (18) Wang, X.; Wang, Y.; Zhang, B.; Zhang, F.; Yang, Z.; Pan, S. CsB4O6F: A Congruent-Melting Deep-Ultraviolet Nonlinear Optical Material by Combining Superior Functional Units. Angew. Chem., Int. Ed. 2017, 56, 14119−14123. (19) Shi, G.; Wang, Y.; Zhang, F.; Zhang, B.; Yang, Z.; Hou, X.; Pan, S.; Poeppelmeier, K. R. Finding the Next Deep-Ultraviolet Nonlinear Optical Material: NH4B4O6F. J. Am. Chem. Soc. 2017, 139, 10645− 10648. (20) Kolb, U.; Gorelik, T.; Kübel, C.; Otten, M. T.; Hubert, D. Towards automated diffraction tomography: Part I-Data acquisition. Ultramicroscopy 2007, 107, 507−513.

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.8b00545. Experimental details (PDF) Crystal structure information (CIF)

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AUTHOR INFORMATION

Corresponding Authors

*J. Sun. E-mail: [email protected]. *Z. Lin. E-mail: [email protected]. ORCID

Fei Liang: 0000-0002-4932-1329 Tao Yang: 0000-0002-2276-4023 Rihong Cong: 0000-0002-9018-6819 Zheshuai Lin: 0000-0002-9829-9893 Junliang Sun: 0000-0003-4074-0962 Author Contributions #

Zhengyang Zhou, Yi Qiu and Fei Liang contributed equally to this work. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by China “863” Project (No. 2015AA034203), the National Basic Research Program (No. 2013CB933402, 2016YFA0301004) and National Natural Science Foundation of China (No. 21771027, 21671028, 21527803, 21471009, 21621061, 91622118). Z.-S. Lin. acknowledges the support from Youth Innovation Promotion Association Chinese Academy of Sciences. Z. Zhou acknowledges the support from China Scholarship Council. 2206

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Communication

Chemistry of Materials (21) Kolb, U.; Gorelik, T.; Otten, M. T. Towards automated diffraction tomography. Part II-Cell parameter determination. Ultramicroscopy 2008, 108, 763−772. (22) Mugnaioli, E.; Gorelik, T.; Kolb, U. Ab initio” structure solution from electron diffraction data obtained by a combination of automated diffraction tomography and precession technique. Ultramicroscopy 2009, 109, 758−765. (23) Zhang, D.; Oleynikov, P.; Hovmöller, S.; Zou, X. Collecting 3D electron diffraction data by the rotation method. Z. Kristallogr. 2010, 225, 94−102. (24) Wan, W.; Sun, J.; Su, J.; Hovmoller, S.; Zou, X. Threedimensional rotation electron diffraction: software RED for automated data collection and data processing. J. Appl. Crystallogr. 2013, 46, 1863−1873. (25) Nannenga, B. L.; Shi, D.; Leslie, A. G. W.; Gonen, T. Highresolution structure determination by continuous-rotation data collection in MicroED. Nat. Methods 2014, 11, 927−930. (26) Gemmi, M.; La Placa, M. G. I.; Galanis, A. S.; Rauch, E. F.; Nicolopoulos, S. Fast electron diffraction tomography. J. Appl. Crystallogr. 2015, 48, 718−727. (27) Jiang, J.; Jorda, J. L.; Yu, J.; Baumes, L. A.; Mugnaioli, E.; DiazCabanas, M. J.; Kolb, U.; Corma, A. Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ43. Science 2011, 333, 1131−1134. (28) Willhammar, T.; Sun, J.; Wan, W.; Oleynikov, P.; Zhang, D.; Zou, X.; Moliner, M.; Gonzalez, J.; Martínez, C.; Rey, F.; Corma, A. Structure and catalytic properties of the most complex intergrown zeolite ITQ-39 determined by electron crystallography. Nat. Chem. 2012, 4, 188−194. (29) Chen, H.; Ju, J.; Meng, Q.; Su, J.; Lin, C.; Zhou, Z.; Li, G.; Wang, W.; Gao, W.; Zeng, C.; Tang, C.; Lin, J.; Yang, T.; Sun, J. PKU3: An HCl-Inclusive Aluminoborate for Strecker Reaction Solved by Combining RED and PXRD. J. Am. Chem. Soc. 2015, 137, 7047−7050. (30) Yun, Y.; Zou, X.; Hovmoller, S.; Wan, W. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders. IUCrJ 2015, 2, 267−282. (31) Palatinus, L.; Petricek, V.; Correa, C. A. Structure refinement using precession electron diffraction tomography and dynamical diffraction: theory and implementation. Acta Crystallogr., Sect. A: Found. Adv. 2015, 71, 235−244. (32) Palatinus, L.; Correa, C. A.; Steciuk, G.; Jacob, D.; Roussel, P.; Boullay, P.; Klementova, M.; Gemmi, M.; Kopecek, J.; Domeneghetti, M. C.; Camara, F.; Petricek, V. Structure refinement using precession electron diffraction tomography and dynamical diffraction: tests on experimental data. Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater. 2015, 71, 740−751. (33) Palatinus, L.; Brázda, P.; Boullay, P.; Perez, O.; Klementová, M.; Petit, S.; Eigner, V.; Zaarour, M.; Mintova, S. Hydrogen positions in single nanocrystals revealed by electron diffraction. Science 2017, 355, 166−169. (34) Chen, C.; Sasaki, T.; Li, R.; Wu, Y.; Lin, Z.-S.; Mori, Y.; Hu, Z.; Wang, J.; Uda, S.; Yoshimura, M.; Kaneda, Y. Nonlinear Optical Borate Crystals: Principles and Applications; Wiley-VCH Verlag GmbH & Co. KGaA, 2012. (35) Wu, H.; Yu, H.; Pan, S.; Huang, Z.; Yang, Z.; Su, X.; Poeppelmeier, K. R. Cs2B4SiO9: A Deep-Ultraviolet Nonlinear Optical Crystal. Angew. Chem., Int. Ed. 2013, 52, 3406−3410. (36) Derkacheva, E. S.; Krzhizhanovskaya, M. G.; Bubnova, R. S.; Filatov, S. K. Transformation of the Crystal Structure in the Series of K1−xCsxBSi2O6 Borosilicate Solid Solutions. Glass Phys. Chem. 2011, 37, 572−578. (37) Kong, F.; Jiang, H.-L.; Hu, T.; Mao, J.-G. CsB3GeO7 and K2B2Ge3O10: Explorations of New Second-Order Nonlinear Optical Materials in the Borogermanate Systems. Inorg. Chem. 2008, 47, 10611−10617. (38) Zhang, J.-H.; Hu, C.-L.; Xu, X.; Kong, F.; Mao, J.-G. New Second-Order NLO Materials Based on Polymeric Borate Clusters

and GeO4 Tetrahedra: A Combined Experimental and Theoretical Study. Inorg. Chem. 2011, 50, 1973−1982. (39) Palatinus, L.; Chapuis, G. SUPERFLIP - a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions. J. Appl. Crystallogr. 2007, 40, 786−790. (40) Brown, I. D.; Altermatt, D. Bond-valence parameters obtained from a systematic analysis of the Inorganic Crystal Structure Database. Acta Crystallogr., Sect. B: Struct. Sci. 1985, 41, 244−247. (41) Brese, N. E.; O’Keeffe, M. Bond-valence parameters for solids. Acta Crystallogr., Sect. B: Struct. Sci. 1991, 47, 192−197. (42) Kurtz, S. K.; Perry, T. T. A Powder Technique for the Evaluation of Nonlinear Optical Materials. J. Appl. Phys. 1968, 39, 3798−3813. (43) Kohn, W. Nobel Lecture: Electronic structure of matter-wave functions and density functionals. Rev. Mod. Phys. 1999, 71, 1253− 1266. (44) Wang, C. S.; Klein, B. M. First-principles electronic structure of Si, Ge, GaP, GaAs, ZnS, and ZnSe. II. Optical properties. Phys. Rev. B: Condens. Matter Mater. Phys. 1981, 24, 3417−3429. (45) Lee, M.-H.; Yang, C.-H.; Jan, J.-H. Band-resolved analysis of nonlinear optical properties of crystalline and molecular materials. Phys. Rev. B: Condens. Matter Mater. Phys. 2004, 70, 235110. (46) He, R.; Lin, Z.-S.; Lee, M. H.; Chen, C. T. Ab initio studies on the mechanism for linear and nonlinear optical effects in YAl3(BO3)4. J. Appl. Phys. 2011, 109, 103510. (47) Wu, B.; Xie, F.; Chen, C.; Deng, D.; Xu, Z. Generation of tunable coherent vacuum ultraviolet radiation in LiB3O5 crystal. Opt. Commun. 1992, 88, 451−454. (48) Jackson, A. G.; Ohmer, M. C.; LeClair, S. R. Relationship of the second order nonlinear optical coefficient to energy gap in inorganic non-centrosymmetric crystals. Infrared Phys. Technol. 1997, 38, 233− 244. (49) Lin, J.; Lee, M.-H.; Liu, Z.-P.; Chen, C.; Pickard, C. J. Mechanism for linear and nonlinear optical effects in β-BaB2O4 crystals. Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 60, 13380− 13389.

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DOI: 10.1021/acs.chemmater.8b00545 Chem. Mater. 2018, 30, 2203−2207