During my academic years, I published 14 peer-reviewed papers in high-quality scientific journals, presented at international conferences, and mentored junior researchers. Currently, I work in the industry and have several patents granted or in the pipeline.
Liu, Z., (2023) U.S. Patent No. 11,694,477
Liu, Z., Ton-That, C.-H. (2022) U.S. Patent No. 11,443,553
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V. Adhikari, Z. T. Y. Liu, N. J. Szymanski, I. Khatri, D. Gall, P. Sarin, S. V. Khare, J. Phys. Chem. Solids, 120, 197-206 (2018)
We report results from systematic calculations performed by density functional theory on mechanical properties of twenty-eight 3 d, 4 d and 5 d transition metal (M) nitrides (TMNs) in metal-rich cubic M4N structure as novel candidates for hard coatings materials.
13. Universal link of magnetic exchange and structural behavior under pressure in chromium spinels
I. Efthimiopoulos, I. Khatri, Z. T. Y. Liu, S. V. Khare, P. Sarin, V. Tsurkan, A. Loidl, D. Zhang, Y. Wang, Phys. Rev. B, 97, 184435 (2018)
We have conducted high-pressure x-ray diffraction studies on spinels at room temperature. Both compounds undergo pressure-induced structural transitions into diverse tetragonal modifications.
12. Electronic and optical properties of vanadium oxides from first principles
N.J. Szymanski, Z. T. Y. Liu, T. Alderson, P. Sarin, S. V. Khare, Comput. Mater. Sci. 146, 310-318 (2018)
We have studied the structural, energetic, electronic, and optical properties of six compounds belonging to the system of vanadium oxides, including both high- and low-temperature phases, obtained using first principles calculations based on density functional theory.
11. Transparency enhancement for SrVO\(_3\) by SrTiO\(_3\) mixing: A first-principles study
Z. T. Y. Liu, N. J. Podraza, S. V. Khare, P. Sarin, Comput. Mater. Sci. 144, 139-146 (2018)
We have studied the mixing of SrVO\(_3\) and SrTiO\(_3\) with ab initio based simulation methods. We confirmed feasibility of obtaining full-composition-range solid solutions SrTi\(_{1-x}\)V\(_x\)O\(_3\). Substitution of V with Ti reduces electrical conductivity to negligible level at x = 0.67. Such substitution suppresses the optical absorption beyond 3.25 eV. Doping/vacancy creation could enhance conductivity while allowing for optical tuning.
Z. T. Y. Liu, B. P. Burton, S. V. Khare, D. Gall, J. Phys.-Condens. Matter, 29, 035401 (2016)
We have studied the phase equilibria of three ceramic quasibinary systems Ti\(_{1-x}\)Zr\(_x\)N, Ti\(_{1-x}\)Hf\(_x\)N and Zr\(_{1-x}\)Hf\(_x\)N (0 ≤ x ≤ 1) with density functional theory, cluster expansion and Monte Carlo simulations. We predict consolute temperatures (\(T_{C}\)), at which miscibility gaps close, for Ti\(_{1-x}\)Zr\(_x\)N to be 1400 K, for Ti\(_{1-x}\)Hf\(_x\)N to be 700 K, and below 200 K for Zr\(_{1-x}\)Hf\(_x\)N.
9. Pressure-induced phase transitions in the CdCr\(_2\)Se\(_4\) spinel
I. Efthimiopoulos, Z. T. Y. Liu, M. Kucway, S. V. Khare, P. Sarin, V. Tsurkan, A. Loidl, and Y. Wang, Phys. Rev. B, 94, 174106 (2016)
We have conducted high-pressure x-ray diffraction and Raman spectroscopic studies on the CdCr\(_2\)Se\(_4\) spinel at room temperature up to 42 GPa. We have resolved three structural transitions up to 42 GPa, i.e., the starting Fd-3m phase transforms at -11 GPa into a tetragonal I41/amd structure, an orthorhombic distortion was observed at -15 GPa, whereas structural disorder initiates beyond 25 GPa. Our ab initio density functional theory studies successfully reproduced the observed crystalline-to-crystalline structural transitions.
Z. T. Y. Liu, B. P. Burton, S. V. Khare, P. Sarin, Chem. Geol. 443, 137-145 (2016)
Quasibinary solid solutions of calcite-structure carbonate minerals play an important role in rock formation. We have investigated solid solutions with cations Ca\(^{2+}\), Cd\(^{2+}\), Mg\(^{2+}\) and Zn\(^{2+}\) by performing first-principles phase diagram calculations for Ca\(_{1-x}\)Zn\(_x\)CO\(_3\), Cd\(_{1-x}\)Zn\(_x\)CO\(_3\), Ca\(_{1-x}\)Cd\(_x\)CO\(_3\) and Mg\(_{1-x}\)Zn\(_x\)CO\(_3\) (0 ≤ x ≤ 1) with density functional theory, cluster expansion and Monte Carlo simulations.
7. Structural transition in the magnetoelectric ZnCr\(_2\)Se\(_4\) spinel under pressure
I. Efthimiopoulos, Z. T. Y. Liu, S. V. Khare, P. Sarin, V. Tsurkan, A. Loidl, D. Popov and Y. Wang, Phys. Rev. B 93, 174103 (2016)
Τhe magnetoelectric ZnCr\(_2\)Se\(_4\) spinel, with space group Fd-3m, undergoes a reversible first-order structural transition initiating at 17 GPa, as revealed by our high-pressure X-ray diffraction studies at room temperature. Our density functional theory calculations successfully reproduce the structural transition.
6. Thermal Equation of State of Silicon Carbide
Y. Wang, Z. T. Y. Liu, S. V. Khare, S. A. Collins, J. Zhang, L. Wang and Y. Zhao, Appl. Phys. Lett. 108, 061906 (2016)
A large volume press coupled with in-situ energy-dispersive synchrotron X-ray was used to probe the change of silicon carbide (SiC) under high pressure and temperature (P-T) up to 8.1 GPa and 1100 K. The obtained pressure–volume–temperature data were fitted to a modified high-T Birch-Murnaghan equation of state, yielding values of a series of thermo-elastic parameters. In addition, the elastic properties of SiC were determined by density functional theory through the calculation of Helmholtz free energy.
5. Pressure-induced transition in the multiferroic CoCr\(_2\)O\(_4\) spinel
I. Efthimiopoulos, Z. T. Y. Liu, S. V. Khare, P. Sarin, T. Lochbiler, V. Tsurkan, A. Loidl, D. Popov, and Y. Wang, Phys. Rev. B, 92, 064108 (2015)
We have explored the high-pressure structural, vibrational, electronic, and magnetic behavior of the multiferroic CoCr\(_2\)O\(_4\) spinel up to 30 GPa by means of X-ray diffraction, Raman spectroscopy, and density functional theory calculations. Our investigations revealed a reversible tetragonal distortion of the starting cubic structure above 16 GPa. We suggest that the structural modification is mainly driven by magnetic effects induced under pressure.
4. Electronic and bonding analysis of hardness in pyrite-type transition-metal pernitrides
Z. T. Y. Liu, D. Gall and S. V. Khare, Phys. Rev. B 90, 134102 (2014)
We answer the question of the exceptional mechanical properties of pyrite-type PtN\(_2\) by a systematic computational analysis of it and other pyrite-type transition-metal pernitrides MN\(_2\) with density functional theory.
J. L. Roehl, Z. T. Y. Liu and S. V. Khare, Mater. Res. Express 1, 025904 (2014)
We present an ab initio study of the diffusion profiles in CdS of native, Cd and S vacancies, and interstitial adatoms Cd, S, Te, Cu, and Cl.
Z. T. Y. Liu, X. Zhou, D. Gall and S. V. Khare, Comput. Mater. Sci. 84, 365 (2014)
We have performed ab initio calculations on 29 nitride phases of transition metals from the 3d, 4d and 5d rows, in NbO structure. We calculated cohesive energy, lattice constant and elastic constants \(C_{11}\), \(C_{12}\) and \(C_{44}\), and derived mechanical moduli, related ratios and Vickers hardness.
Z. T. Y. Liu, X. Zhou, S. V. Khare and D. Gall, J. Phys.-Condens. Matter 26, 025404 (2014)
We report systematic results from ab initio calculations with density functional theory on three cubic structures, zincblende (zb), rocksalt (rs) and cesium chloride (cc), of the ten 3d transition metal nitrides. We computed lattice constants, elastic constants, their derived mechanical moduli, ratios and Vickers hardness.