Non-centrosymmetric (NCS) materials, those that do not contain an inversion center, exhibit a variety of important functional properties. These include, ferroelectricity, pyroelectricity, piezoelectricity, and second-harmonic generation. A Venn diagram depicting the relationships between acentric crystal class and physical property is shown below.

Our interest is in not only discovering new NCS materials, but also understanding their structure-property relationships. We have focused on synthesizing new NCS materials by utilizing cations susceptible to second-order Jahn-Teller (SOJT) distortions, i.e. octahedrally coordinated d⁰ transition metals (Ti⁴⁺, Nb⁵⁺, W⁶⁺, etc.), and cations with a stereo-active lone-pair (Sn²⁺, Se⁴⁺, Te⁴⁺, etc.). In doing so, we have synthesized and characterized a variety of new NCS compounds. More recently, we are focusing on NCS materials with deep UV NLO applications, i.e., where the absorption edge is less than 200nm. We have an ongoing collaboration with Prof. James Rondinelli (Northwestern University - http://mtd.mccormick.northwestern.edu/) to investigate the atomic distortions in these materials.

Recent Publications

• Yu, H., Young, J., Wu, H., Zhang, W., Rondinelli, J.M., and Halasyamani, P.S., M₄Mg₄(P₂O₇)₃ (M = K, Rb): Structural Engineering of Pyrophosphates for NLO Applications, Chem. Mater., Chem. Mater., 29, 1845-1855, 2017.
• Wu, H., Yu, H., Zhang, W., Cantwell, J., Poeppelmeier, K.R., Pan, S., and Halasyamani, P.S., Top-Seeded Solution Crystal Growth, Linear and Nonlinear Optical Properties of Ba₄B₁₁O₂₀F (BBOF), Cryst. Growth Des., 17, 1404-1410, 2017.
• Tran, T.T., Koocher, N.Z., Rondinelli, J.M., and Halasyamani, P.S., Be-free β-Rb₂Al₂B₂O₇ (β-RABO) as a Possible Deep-Ultraviolet Nonlinear Optical Material Replacement for KBe₂BO₃F₂ (KBBF), Angew. Chemie, 56, 2969-2973, 2017.
• Olchowka, J., Colmont, M., Aliev, A., Tran, T.T., Halasyamani, P.S., Hagemann, H.R., and Mentré, O., New oxo-centered bismuth oxo-arsenates; Critical effect of PO₄ for AsO₄ substitution, CrystEngComm, 19, 936-945, 2017.
• Tran, T.T., Young, J., Rondinelli, J.M., and Halasyamani, P.S., Mixed-Metal Carbonate Fluorides as Deep-Ultraviolet Non-linear Optical Materials, J. Am. Chem. Soc., 139, 1285-1295, 2017.
• Tran, T.T., Yu, H., Rondinelli, J.R., Poeppelmeier, K.R., and Halasyamani, P.S., Deep Ultraviolet Nonlinear Optical Materials, Chem. Mater., 28, 5238-5258, 2016.
• Yu, H., Young, J., Wu, H., Zhang, W., Rondinelli, J.M., and Halasyamani, P.S., Electronic, Crystal Chemistry, and Nonlinear Optical Property Relationships in the Dugganite A₃B₃CD₂O₁₄ Family (A = Sr, Ba or Pb; B = Mg or Zn; C = Te or W, and D = P or V), J. Am. Chem. Soc., 138, 4984-4989, 2016.
• Yu, H., Zhang, W., Young, J., Rondinelli, J.M., and Halasyamani, P.S., Bidenticity Enhanced Second Harmonic Generation from Pb-Chelation in Pb₃Mg₃TeP₂O₁₄, J. Am. Chem. Soc., 138, 88-91, 2016.
• Yu, H., Zhang, W., Young, J., Rondinelli, J.M., and Halasyamani, P.S., Design and Synthesis of the Beryllium-Free Deep-Ultraviolet Nonlinear Optical Material Ba₃(ZnB₅O₁₀)PO₄, Adv. Mater., 27, 7380-7385, 2015.
• Tran, T.T., He, J., Rondinelli, J.M., and Halasyamani, P.S., RbMgCO₃F - A New Deep-Ultraviolet Nonlinear Optical Material, J. Am. Chem. Soc., 137, 10504-10507, 2015.
• Yu, H., Wu, H., Jing, Q., Yang, Z., Halasyamani, P.S., and Pan, S., Polar Polymorphism: a-, b-, and g- Pb₂Ba₄Zn₄B₁₄O₃₁ - Synthesis, Characterization, and Nonlinear Optical Properties, Chem. Mater., 27, 4779-4788, 2015.
• Cammarata, A., Zhang, W., Halasyamani, P.S., and Rondinelli, J., Microscopic Origins of Optical Second Harmonic Generation in Noncentrosymmetric-Nonpolar Materials, Chem. Mater., 26, 5773-5781, 2014.
• Thao, T.T., Halasyamani, P.S., and Rondinelli, J., Role of Acentric Displacements on the Crystal Structure and Second-Harmonic Generating Properties of RbPbCO₃F and CsPbCO₃F, Inorg. Chem., 53, 6241-6251, 2014.
• Nguyen, S. D. and Halasyamani, P.S., Synthesis, Structure, and Characterization of Two New Polar Sodium Tungsten Selenites: Na₂(WO₃)₃(SeO₃). 2H₂O and Na₆(W₆O₁₉)(SeO₃)₂, Inorg. Chem., 52, 2637-2647, 2013.
• Tran, Thao T. and Halasyamani, P.S., New Fluoride Carbonates: Centrosymmetric KPb₂(CO₃)₂F and Noncentrosymmetric K_2.70Pb_5.15(CO₃)₅F₃, Inorg. Chem., 52, 2466-2473, 2013.
• Nguyen, S.D. and Halasyamani, P.S., Synthesis, Structures, and Characterization of New Noncentrosymmetric and Polar Li₆(Mo₂O₅)₃(SeO₃) and Centrosymmetric Li₂(MO₃)(TeO₃) (M = Mo⁶⁺ or W⁶⁺), Inorg. Chem., 51, 9529–9538, 2012.
• Yeon, J., Kim, S.-H., Nguyen, S.D., Lee, H., and Halasyamani, P.S., Two New Noncentrosymmetric (NCS) Polar Oxides: Syntheses, Characterization, and Structure-Property Relationships in BaMTe₂O₇ (M = Mg²⁺ or Zn²⁺), Inorg. Chem., 51, 2662-2668, 2012.
• Yeon, J., Kim, S.-H., Nguyen, S., Lee, H., Halasyamani, P.S., New Vanadium Selenites: Centrosymmetric Ca₂(VO₂)₂(SeO₃)₃(H₂O)₂, Sr₂(VO₂)₂(SeO₃)₃, and Ba(V₂O₅)(SeO₃), and Noncentrosymmetric and Polar A₄(VO₂)₂(SeO₃)₄(Se₂O₅) (A = Sr²⁺ or Pb²⁺), Inorg. Chem., 51, 609-619, 2012.
• Nguyen, S. D., Yeon, J., Kim, S.-H., and Halasyamani, P. S., BiO(IO₃): A New Polar Oxide Material, with a Large SHG Response, that contains Two Lone-pair Cations and Exhibits an Aurivillius-type (Bi₂O₂)²⁺ Layer, J. Am. Chem. Soc., 133, 12422-12425, 2011.
• Nguyen, S.D., Kim, S.-H., and Halasyamani, P.S., Synthesis, Characterization, and Structure-Property Relationships in Two New Polar Oxides: Zn₂(MoO₄)(SeO₃) and Zn₂(MoO₄)(TeO₃), Inorg. Chem., 50, 5215–5222, 2011.
• Yeon, J., Kim, S.-H., and Halasyamani, P.S., A₃V₅O₁₄ (A = K⁺, Rb⁺, or Tl⁺): New Polar Oxides with a Tetragonal Tungsten Bronze Related Structural Topology – Synthesis, Structure, and Functional Properties, Inorg. Chem., 49, 6986–6993, 2010.