PNNL

Dr. Kowalski is an expert in advancing electronic structure methods and parallel algorithms for many-body methods, and applying these formalisms to tackle complex chemical processes. Over the last seven years he has been coordinating the development of NWChem computational chemistry software at PNNL. He is recognized for several important contributions he made in the area of coupled cluster (CC) theory including renormalized CC theories, multi-reference formulations, and linear response methods. An important part of his research portfolio is associated with the development of scalable implementations of many-body formulations describing correlated behavior of electrons in molecular systems. In particular, he has developed implementations of quantum chemical methods capable of taking advantage of hundreds of thousands of processors with the concurrent utilization of various types of accelerators. Dr. Kowalski is also an author of new CC Green’s function formulations that are used in high-accuracy characterization of ionization and transport processes in molecules. Currently, Dr. Kowalski is leading BES Quantum Information Science project with the focus on enabling quantum computing for realistic chemical systems and processes.

• Many-body formulations for correlated molecular systems
• Coupled cluster methods for ground- and excited-state problems
• Multireference coupled cluster formulations
• Green’s function methods and embedding approaches
• High-performance computing: peta- and exa-scale implementations of many-body methods
• Quantum computing  - new techniques for dimensionality reduction of many-body Hamiltonians, unitary coupled cluster formulations, and  Green’s function methods 

• Ph.D., Theoretical Physics, Nicolaus Copernicus University, Torun, Poland, 1999
• M.Sc., Theoretical Physics, Nicolaus Copernicus University, Poland, 1991

• Scientist, Pacific Northwest National Laboratory, 2004-Present
• Post Doctoral Researcher, Michigan State University, 1999-2004
• Referee: Various journals on chemistry, quantum chemistry, physical chemistry, and physics 
• Membership: American Chemical Society, 2001-Present

• Pathway to Excellence Award, Pacific Nortwest National Laboratory - 2019
• BESTies Award, Pacific Northwest National Laboratory – 2018
• Pathway to Excellence Award, Pacific Nortwest National Laboratory – 2015
• Journal of Chemical Physics 80^th Anniversary Collection, one of the 80 articles selected – 2013 
• Quantum Theory Project Stipend (Löwdin Award) - 2000
• Award of the Minister of National Education of Poland - 2000

2020

• Apra E., E.J. Bylaska, W.A. De Jong, N. Govind, K. Kowalski, T.P. Straatsma, and M. Valiev, et al. 2020. "NWChem: Past, Present, and Future." The Journal of Chemical Physics 152, no. 18:184102. PNNL-SA-151542. doi:10.1063/5.0004997
• Barca G.M., C. Bertoni, L. Carrington, D. Datta, N. DeSilva, E.J. Deustua, and D. Fedorov, et al. 2020. "Recent Developments in the General Atomic and Molecular Electronic Structure System." Journal of Chemical Physics 152, no. 15:Article No. 154102. PNNL-SA-152270. doi:10.1063/5.0005188
• Peng B., K. Kowalski, A.R. Panyala, and S. Krishnamoorthy. 2020. "Green’s function coupled cluster simulation of the near-valence ionizations of DNA-fragments." Journal of Chemical Physics 152, no. 1:Article No. 011101. PNNL-SA-148915. doi:10.1063/1.5138658
• Rehr J.J., F.D. Vila, J.J. Kas, N. Hirshberg, K. Kowalski, and B. Peng. 2020. "Equation of motion coupled-cluster cumulant approach for intrinsic losses in x-ray spectra." The Journal of Chemical Physics 152, no. 17:Article No. 174113. PNNL-SA-151280. doi:10.1063/5.0004865

2019

• Bauman N.P., E.J. Bylaska, S. Krishnamoorthy, G. Low, N.O. Wiebe, C.E. Granade, and M. Roetteler, et al. 2019. "Downfolding of many-body Hamiltonians using active-space models: extension of the sub-system embedding sub-algebras approach to unitary coupled cluster formalisms." Journal of Chemical Physics 151, no. 1:Article Number 014107. PNNL-SA-141041. doi:10.1063/1.5094643
• Khan M.H., M. Halappanavar, T.J. Hagge, K. Kowalski, A. Pothen, and S. Krishnamoorthy. 2019. "Mapping Arbitrarily Sparse Two-body Interactions on One-dimensional Quantum Circuits." In IEEE 26th International Conference on High Performance Computing, Data, and Analytics (HiPC 2019), December 17-20, Hyderabad, India, 52-62. Los Alamitos, California:IEEE Computer Society. PNNL-SA-144919. doi:10.1109/HiPC.2019.00018
• Mutlu E., K. Kowalski, and S. Krishnamoorthy. 2019. "Toward Generalized Tensor Algebra for ab initio Quantum Chemistry Methods." In Proceedings of th 6th ACM SIGPLAN International Workshop on Libraries, Languages, and Compilers for Array Programming (ARRAY 2019), June 22, 2019, Phoeniz, AZ, 46-56. New York, New York:ACM. PNNL-SA-142686. doi:10.1145/3315454.3329958
• Peng B., R. Van Beeumen, D. Williams-Young, K. Kowalski, and C. Yang. 2019. "Approximate Green’s Function Coupled Cluster A Method Employing Effective Dimension Reduction." Journal of Chemical Theory and Computation 15, no. 5:3185-3196. PNNL-SA-141176. doi:10.1021/acs.jctc.9b00172

2018

• Kowalski K. 2018. "Properties of coupled-cluster equations originating in excitation sub-algebras." Journal of Chemical Physics 148, no. 9:094104. PNNL-SA-130129. doi:10.1063/1.5010693
• Peng B., and K. Kowalski. 2018. "Green's function coupled-cluster approach: simulating photoelectron spectra for realistic molecular systems." Journal of Chemical Theory and Computation 14, no. 8:4335-4352. PNNL-SA-133559. doi:10.1021/acs.jctc.8b00313
• Peng B., and K. Kowalski. 2018. "Green’s function coupled cluster formulations utilizing extended inner excitations." Journal of Chemical Physics 149, no. 21:214102. PNNL-SA-136088. doi:10.1063/1.5046529

2017

• Berardo E., F. Kaplan, K. Bhaskaran Nair, W.A. Shelton, M.J. Van Setten, K. Kowalski, and M.A. Zwijnenburg. 2017. "Benchmarking the Fundamental Electronic Properties of small TiO2 Nanoclusters by GW and Coupled Cluster Theory Calculations." Journal of Chemical Theory and Computation 13, no. 8:3470-3477. PNNL-SA-125647. doi:10.1021/acs.jctc.7b00538
• Bylaska E.J., E. Apra, K. Kowalski, M. Jacquelin, W.A. De Jong, A. Vishnu, and B.J. Palmer, et al. 2017. "Transitioning NWChem to the Next Generation of Manycore Machines." In Exascale Scientific Applications: Scalability and Performance Portability, edited by TP Straatsma, KB Antypas and TJ Williams. 165-186. New York, New York:Chapman and Hall/CRC. PNNL-SA-130902.
• Lang J., M. Svana, O. Demel, J. Brabec, S. Kedzuch, J. Noga, and K. Kowalski, et al. 2017. "A MRCC study of the isomerisation of cyclopropane." Molecular Physics 115, no. 21-22:2743-2754. PNNL-SA-125730. doi:10.1080/00268976.2017.1317112
• Moore B., R. Schrader, K. Kowalski, and J. Autschbach. 2017. "Electronic pi to pi* excitations of rhodamine dyes exhibit a time-dependent Kohn-Sham theory "cyanine problem"." ChemistryOPEN 6, no. 3:385-392. PNNL-SA-125649. doi:10.1002/open.201700046
• Peng B., and K. Kowalski. 2017. "Highly efficient and scalable compound decomposition of two-electron integral tensor and its application in coupled cluster calculations." Journal of Chemical Theory and Computation 13, no. 9:4179-4192. PNNL-SA-126829. doi:10.1021/acs.jctc.7b00605
• Peng B., and K. Kowalski. 2017. "Low-rank factorization of electron integral tensors and its application in electronic structure theory." Chemical Physics Letters 672. PNNL-SA-122607. doi:10.1016/j.cplett.2017.01.056
• Peng B., N. Govind, E. Apra, M. Klemm, J.R. Hammond, and K. Kowalski. 2017. "Coupled Cluster Studies of Ionization Potentials and Electron Affinities of Single-Walled Carbon Nanotubes." Journal of Physical Chemistry A 121, no. 6:1328-1335. PNNL-SA-122228. doi:10.1021/acs.jpca.6b10874
• Pirojsirikul T., A.W. Goetz, J.H. Weare, R.C. Walker, K. Kowalski, and M. Valiev. 2017. "Combined Quantum-Mechanical Molecular Mechanics Calculations with NWChem and AMBER: Excited State Properties of Green Fluorescent Protein Chromophore Analogue in Aqueous Solution." Journal of Computational Chemistry 38, no. 18:1631-1639. PNNL-SA-122946. doi:10.1002/jcc.24804
• Rajbhandari S., F. Rastello, K. Kowalski, S. Krishnamoorthy, and P. Sadayappan. 2017. "Optimizing the Four-Index Integral Transform Using Data Movement Lower Bounds Analysis." In Proceedings of the 22nd ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming (PPoPP 2017), February 4-8, 2017, Austin, Texas, 52, 327-340. New York, New York:ACM. PNNL-SA-122720. doi:10.1145/3155284.3018771

2016

• Bhaskaran-Nair K., K. Kowalski, and W.A. Shelton. 2016. "Coupled Cluster Green function: model involving single and double excitations." Journal of Chemical Physics 144, no. 14:144101. PNNL-SA-114925. doi:10.1063/1.4944960
• Brabec J., S. Banik, K. Kowalski, and J. Pittner. 2016. "Perturbative universal state-selective correction for a state-specific multi-reference coupled cluster methods." Journal of Chemical Physics 145, no. 16:Article No. 164106. PNNL-SA-116405. doi:10.1063/1.4965826
• Hu H., Y. Zhao, J.R. Hammond, E.J. Bylaska, E. Apra, H.J. van Dam, and J. Li, et al. 2016. "Theoretical studies of the global minima and polarizabilities of small lithium clusters." Chemical Physics Letters 644. PNNL-SA-107717. doi:10.1016/j.cplett.2015.11.049
• Ma X., R.W. Hall, F. Loffler, K. Kowalski, K. Bhaskaran-Nair, M. Jarrell, and J. Moreno. 2016. "Sign learning kink-based (SiLK) quantum Monte Carlo for molecular systems." Journal of Chemical Physics 144, no. 1:Article No. 014101. PNNL-SA-112158. doi:10.1063/1.4939145
• Peng B., and K. Kowalski. 2016. "Coupled-cluster Green’s function: analysis of properties originating in the exponential parametrization of the ground-state wave function." Physical Review. A. 94, no. 6:Article No. 062512. PNNL-SA-121797. doi:10.1103/PhysRevA.94.062512

2015

• Apra E., K. Kowalski, J.R. Hammond, and M. Klemm. 2015. "NWChem: Quantum Chemistry Simulations at Scale." In High Performance Parallelism Pearls - Multicore and Many-core Programming Approaches. 287-306. Waltham, Massachusetts:Morgan Kaufmann. PNNL-SA-104436.
• Banik S., L. Ravichandran, J. Brabec, I. Hubac, K. Kowalski, and J. Pittner. 2015. "Iterative universal state selective correction for the Brillouin-Wigner multireference coupled-cluster theory." Journal of Chemical Physics 142, no. 15:Article No. 114106. PNNL-SA-107175. doi:10.1063/1.4914311
• Bhaskaran-Nair K., K. Kowalski, M. Jarrell, J. Moreno, and W.A. Shelton. 2015. "Equation of motion coupled cluster methods for electron attachment and ionization potential in polyacenes." Chemical Physics Letters 641. PNNL-SA-107107. doi:10.1016/j.cplett.2015.10.071
• Bhaskaran-Nair K., M. Valiev, S. Deng, W.A. Shelton, K. Kowalski, and X.B. Wang. 2015. "Probing microhydration effect on the electronic structure of the GFP chromophore anion: Photoelectron spectroscopy and theoretical investigations." Journal of Chemical Physics 143, no. 22:Article No. 224301. PNNL-SA-113513.
• Moore B., H. Sun, N. Govind, K. Kowalski, and J. Autschbach. 2015. "Charge-Transfer Versus Charge-Transfer-Like Excitations Revisited." Journal of Chemical Theory and Computation 11, no. 7:3305-3320. PNNL-SA-109353. doi:10.1021/acs.jctc.5b00335

2014

• Anisimov V., G.H. Bauer, K. Chadalavada, R.M. Olson, J.W. Glenski, W.T. Kramer, and E. Apra, et al. 2014. "Optimization of the Coupled Cluster Implementation in NWChem on Petascale Parallel Architectures." Journal of Chemical Theory and Computation 10, no. 10:4307-4316. PNNL-SA-99193. doi:10.1021/ct500404c
• Apra E., M. Klemm, and K. Kowalski. 2014. "Efficient Implementation of Many-body Quantum Chemical Methods on the Intel Xeon Phi Coprocessor." In International Conference for High Performance Computing, Networking, Storage and Analysis (SC14), November 16-21, 2014, New Orleans, Louisiana, 674-684. Piscataway, New Jersey:IEEE. PNNL-SA-102322. doi:10.1109/SC.2014.60
• Berardo E., H. Hu, H.J. van Dam, S.A. Shevlin, S.M. Woodley, K. Kowalski, and M.A. Zwijnenburg. 2014. "Describing excited state relaxation and localization in TiO2 nanoparticles using TD-DFT." Journal of Chemical Theory and Computation 10, no. 12:5538-5548. PNNL-SA-105025. doi:10.1021/ct500787x
• Berardo E., H. Hu, S.A. Shevlin, S.M. Woodley, K. Kowalski, and M.A. Zwijnenburg. 2014. "Modeling Excited States in TiO2 Nanoparticles: On the Accuracy of a TD-DFT Based Description." Journal of Chemical Theory and Computation 10, no. 3:1189-1199. PNNL-SA-99856. doi:10.1021/ct4010273
• Bhaskaran-Nair K., K. Kowalski, J. Moreno, M. Jarrell, and W.A. Shelton. 2014. "Equation of motion coupled cluster methods for electron attachment and ionization potential in fullerenes C60 and C70." Journal of Chemical Physics 141, no. 7:Article No. 074304. PNNL-SA-101921. doi:10.1063/1.4891934
• Hu H., K. Bhaskaran-Nair, E. Apra, N. Govind, and K. Kowalski. 2014. "Toward enabling large-scale open-shell equation-of-motion coupled cluster calculations: triplet states of ß-carotene." Journal of Physical Chemistry A 118, no. 39:9087-9093. PNNL-SA-101464. doi:10.1021/jp5021214
• Kowalski K., K. Bhaskaran-Nair, and W.A. Shelton. 2014. "Coupled-cluster representation of Green function employing modified spectral resolutions of similarity transformed Hamiltonians." Journal of Chemical Physics 141, no. 9:Article No. 094102. PNNL-SA-102874. doi:10.1063/1.4893527
• Pederzoli M., L. Sobek, J. Brabec, K. Kowalski, L. Cwiklik, and J. Pittner. 2014. "Fluorescence of PRODAN in Water: a Computational QM/MM MD Study." Chemical Physics Letters 597. PNNL-SA-92673. doi:10.1016/j.cplett.2014.02.031

2013

• Berardo E., H. Hu, K. Kowalski, and M.A. Zwijnenburg. 2013. "Coupled cluster calculations on TiO2 nanoclusters." Journal of Chemical Physics 139, no. 6:Article No. 064313. PNNL-SA-96066. doi:10.1063/1.4817536
• Bhaskaran-Nair K., and K. Kowalski. 2013. "Bridging single and multireference coupled cluster theories with universal state selective formalism." Journal of Chemical Physics 138, no. 20:Article No. 204114. PNNL-SA-93955. doi:10.1063/1.4806768
• Bhaskaran-Nair K., W. Ma, S. Krishnamoorthy, O. Villa, H.J. van Dam, E. Apra, and K. Kowalski. 2013. "Noniterative Multireference Coupled Cluster Methods on Heterogeneous CPU-GPU Systems." Journal of Chemical Theory and Computation 9, no. 4:1949-1957. PNNL-SA-92866.
• Hu H., and K. Kowalski. 2013. "Excitation energies with cost-reduced variant of the active-space EOMCCSDT method: the EOMCCSDt-(3) over-bar approach." Journal of Chemical Theory and Computation 9, no. 11:4761-4768. PNNL-SA-96343. doi:10.1021/ct400501z
• Ma W., S. Krishnamoorthy, O. Villa, K. Kowalski, and G. Agrawal. 2013. "Optimizing Tensor Contraction Expressions for Hybrid CPU-GPU Execution." Cluster Computing 16, no. 1:131-155. PNNL-SA-79187. doi:10.1007/s10586-011-0179-2
• Tecmer P., N. Govind, K. Kowalski, W.A. De Jong, and L. Visscher. 2013. "Reliable Modeling of the Electronic Spectra of Realistic Uranium Complexes." Journal of Chemical Physics 139, no. 3:Article No. 034301. PNNL-SA-94589. doi:10.1063/1.4812360

2012

• Bhaskaran-Nair K., and K. Kowalski. 2012. "Note: Excited State Studies of Ozone using State-Specific Multireference Coupled Cluster Methods." Journal of Chemical Physics 137, no. 21:Article No. 216101. PNNL-SA-90742. doi:10.1063/1.4769775
• Bhaskaran-Nair K., J. Brabec, E. Apra, H.J. van Dam, J. Pittner, and K. Kowalski. 2012. "Implementation of the multireference Brillouin-Wigner and Mukherjee’s coupled cluster methods with non-iterative triple excitations utilizing reference-level parallelism." Journal of Chemical Physics 137, no. 9:094112-1 to 094112-12. PNNL-SA-88195. doi:10.1063/1.4747698
• Brabec J., H.J. van Dam, J. Pittner, and K. Kowalski. 2012. "Universal state-selective corrections to multireference coupled-cluster theories with single and double excitations." Journal of Chemical Physics 136, no. 12:Article No. 124102. PNNL-SA-83264. doi:10.1063/1.3692969
• Brabec J., J. Pittner, H.J. van Dam, E. Apra, and K. Kowalski. 2012. "Parallel implementation of multireference coupled-cluster theories based on the reference-level parallelism." Journal of Chemical Theory and Computation 8, no. 2:487-497. PNNL-SA-84133.
• Brabec J., K. Bhaskaran-Nair, K. Kowalski, J. Pittner, and H.J. van Dam. 2012. "Towards large-scale calculations with State-Specific Multireference Coupled Cluster methods: Studies on dodecane, naphthynes, and polycarbenes." Chemical Physics Letters 542. PNNL-SA-85744. doi:10.1016/j.cplett.2012.05.064
• Brabec J., K. Bhaskaran-Nair, N. Govind, J. Pittner, and K. Kowalski. 2012. "Communication: Application of state-specific multireference coupled cluster methods to core-level excitations." Journal of Chemical Physics 137, no. 17:Article No.171101. PNNL-SA-90515. doi:10.1063/1.4764355
• Hou G., H. Wen, K.A. Lopata, W. Zheng, K. Kowalski, N. Govind, and X.B. Wang, et al. 2012. "A Combined Gas-Phase Photoelectron Spectroscopic and Theoretical Study of Zeise's Anion and Its Bromine and Iodine Analogues." Angewandte Chemie International Edition 51, no. 26:6356-6360. PNNL-SA-86382. doi:10.1002/anie.201201959

2011

• Ali N., S. Krishnamoorthy, N. Govind, K. Kowalski, and P. Sadayappan. 2011. "Application-Specific Fault Tolerance via Data Access Characterization." In Proceedings of the 17th International European Conference on Parallel and Distributed Computing, (Euro-Par 2011), August 29-September 2, 2011, Bordeaux, France. Lecture Notes in Computer Science, edited by E Jeannot, R Namyst and J Roman, 6853, 340-352. Berlin:Springer-Verlag. PNNL-SA-79368. doi:10.1007/978-3-642-23397-5
• Brabec J., S. Krishnamoorthy, H.J. van Dam, K. Kowalski, and J. Pittner. 2011. "Massively parallel implementation of the multi-reference Brillouin-Wigner CCSD method." Chemical Physics Letters 514, no. 4-6:347-351. PNNL-SA-80263. doi:10.1016/j.cplett.2011.08.016
• Campbell C.T., A.K. Datye, G.A. Henkelman, R.F. Lobo, W.F. Schneider, L.D. Spicer, and W.T. Tysoe, et al. 2011. EMSL and Institute for Integrated Catalysis (IIC) Catalysis Workshop. PNNL-20426. Richland, WA: Pacific Northwest National Laboratory. EMSL and Institute for Integrated Catalysis (IIC) Catalysis Workshop
• Govind N., E.J. Bylaska, W.A. De Jong, K. Kowalski, T. Straatsma, M. Valiev, and H.J. van Dam. 2011. "NWChem." In Encyclopedia of Parallel Computing, edited by D Padua. 1345-1353. New York, New York:Springer. PNNL-SA-75220.
• Govind N., K.A. Lopata, R.J. Rousseau, A. Andersen, and K. Kowalski. 2011. "Visible Light Absorption of N-Doped TiO2 Rutile Using (LR/RT)-TDDFT and Active Space EOMCCSD Calculations." The Journal of Physical Chemistry Letters 2, no. 21:2696-2701. PNNL-SA-82229. doi:10.1021/jz201118r
• Kowalski K. 2011. "A universal state-selective approach to multireference coupled-cluster non-iterative corrections." Journal of Chemical Physics 134, no. 19:Article No. 194107. PNNL-SA-76592. doi:10.1063/1.3589896
• Kowalski K., R.M. Olson, S. Krishnamoorthy, V. Tipparaju, and E. Apra. 2011. "Role of Many-Body Effects in Describing Low-Lying Excited States of pi-Conjugated Chromophores: High-Level Equation-of-Motion Coupled-Cluster Studies of Fused Porphyrin Systems." Journal of Chemical Theory and Computation 7, no. 7:2200-2208. PNNL-SA-78691. doi:10.1021/ct200217y
• Kowalski K., S. Krishnamoorthy, R.M. Olson, V. Tipparaju, and E. Apra. 2011. "Scalable implementations of accurate excited-state coupled cluster theories: application of high-level methods to porphyrin based systems." In Proceedings of International Conference for High Performance Computing, Networking, Storage and Analysis (SC'11), November 12-18, 2011, Seattle, Washington, Article No. 72. New York, New York:Association for Computing Machinery. PNNL-SA-78956. doi:10.1145/2063384.2063481
• Lopata K.A., R. Reslan, M.I. Kowalska, D. Neuhauser, N. Govind, and K. Kowalski. 2011. "Excited-state studies of polyacenes: A comparative picture using EOMCCSD, CR-EOMCCSD(T), range-separated (LR/RT)-TDDFT, TD-PM3 and TD-ZINDO." Journal of Chemical Theory and Computation 7, no. 11:3686-3693. PNNL-SA-81719.
• Ma W., S. Krishnamoorthy, O. Villa, and K. Kowalski. 2011. "GPU-based implementations of the noniterative regularized-CCSD(T) corrections: applications to strongly correlated systems." Journal of Chemical Theory and Computation 7, no. 5:1316-1328. PNNL-SA-74991. doi:10.1021/ct1007247
• van Dam H.J., W.A. De Jong, E.J. Bylaska, N. Govind, K. Kowalski, T. Straatsma, and M. Valiev. 2011. "NWChem: scalable parallel computational chemistry." Wiley Interdisciplinary Reviews. Computational Molecular Science 1, no. 6:888-894. PNNL-SA-76231. doi:10.1002/wcms.62

2010

• De Jong W.A., E.J. Bylaska, N. Govind, C.L. Janssen, K. Kowalski, T. Muller, and I. Nielsen, et al. 2010. "Utilizing High Performance Computing for Chemistry: Parallel Computational Chemistry." Physical Chemistry Chemical Physics. PCCP 12, no. 26:6896-6920. PNNL-SA-71071.
• Glaesemann K.R., N. Govind, S. Krishnamoorthy, and K. Kowalski. 2010. "EOMCC, MRPT, and TDDFT Studies of Charge Transfer Processes in Mixed-Valence Compounds: Application to the Spiro Molecule." Journal of Physical Chemistry A 114, no. 33:8764-8771. PNNL-SA-71344. doi:10.1021/jp101761d
• Govind N., R.J. Rousseau, A. Andersen, and K. Kowalski. 2010. "Visible-Light Photoresponse of Nitrogen-Doped TiO2: Excited State Studies using Time-Dependent Density Functional Theory and Equation-of-Motion Coupled Cluster Methods." In Materials Research Society Symposium Proceedings, Symposium Y: Computational Approaches to Materials for Energy, 1263, Paper No. 1263-Y04-06. Warrendale, Pennsylvania:Materials Research Society. PNNL-SA-71824. doi:10.1557/PROC-1263-Y04-06
• Kowalski K., S. Krishnamoorthy, O. Villa, J.R. Hammond, and N. Govind. 2010. "Active-space completely-renormalized equation-of-motion coupled-cluster formalism: Excited-state studies of green fluorescent protein, free-base porphyrin, and oligoporphyrin dimer." Journal of Chemical Physics 132, no. 15:Article Number: 154103. PNNL-SA-68983.
• Ma W., S. Krishnamoorthy, O. Villa, and K. Kowalski. 2010. "Acceleration of Streamed Tensor Contraction Expressions on GPGPU-based Clusters." In Proceedings of the IEEE International Conference on Cluster Computing (CLUSTER 2010), 207-216. Piscataway, New Jersey:Institute of Electrical and Electronic Engineers. PNNL-SA-73012. doi:10.1109/CLUSTER.2010.26
• Valiev M., E.J. Bylaska, N. Govind, K. Kowalski, T. Straatsma, H.J. van Dam, and D. Wang, et al. 2010. "NWChem: a Comprehensive and Scalable Open-Source Solution for Large Scale Molecular Simulations." Computer Physics Communications 181, no. 9:1477-1489. PNNL-SA-66553. doi:10.1016/j.cpc.2010.04.018
• Wang X.B., K. Kowalski, L.S. Wang, and S.S. Xantheas. 2010. "Stepwise hydration of the cyanide anion: A temperature-controlled photoelectron spectroscopy and ab initio computational study of CN-(H2O)n(n=2-5)." Journal of Chemical Physics 132, no. 12:124306/1-10. PNNL-SA-69676. doi:10.1063/1.3360306

2009

• Govind N., M. Valiev, L. Jensen, and K. Kowalski. 2009. "Excitation Energies of Zinc Porphyrin in Aqueous Solution Using Long-Range Corrected Time-Dependent Density Functional Theory." Journal of Physical Chemistry A 113, no. 21:6041-6043. PNNL-SA-65173. doi:10.1021/jp902118k
• Hammond J.R., and K. Kowalski. 2009. "Parallel Computation of Coupled Cluster Hyperpolarizabilities." Journal of Chemical Physics 130, no. 19:Art. No. 194108. PNNL-SA-64764.
• Hammond J.R., N. Govind, K. Kowalski, J. Autschbach, and S.S. Xantheas. 2009. "Accurate dipole polarizabilities for water clusters n=2-12 at the coupled-cluster level of theory and benchmarking of various density functionals." Journal of Chemical Physics 131, no. 21:Article Number:214103. PNNL-SA-67697.
• Kowalski K. 2009. "Nested Variant of the Method of Moments of Coupled Cluster Equations for Vertical Excitation Energies and Excited-state Potential Energy Surfaces." Journal of Chemical Physics 130, no. 19:Art. No. 194110. PNNL-SA-64359.
• Kowalski K., and M. Valiev. 2009. "Extensive regularization of the coupled cluster methods based on the generating functional formalism: application to gas-phase benchmarks and to the S(N)2 reaction of CHCl3 and OH- in water." Journal of Chemical Physics 131, no. 23:Article Number 234107. PNNL-SA-67688.
• Kowalski K., and P. Fan. 2009. "Generating Functionals Based Formulation of the Method of Moments of Coupled Cluster Equations." Journal of Chemical Physics 130, no. 8:Art No. 084112. PNNL-SA-61997.
• Wang X.B., J.C. Werhahn, L.S. Wang, K. Kowalski, A. Laubereau, and S.S. Xantheas. 2009. "Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster." Journal of Physical Chemistry A 113, no. 35:9579-9584. PNNL-SA-67173.

2008

• Epifanovsky E., K. Kowalski, P. Fan, M. Valiev, S. Matsika, and A. Krylov. 2008. "On the Electronically Excited States of Uracil." Journal of Physical Chemistry A 112, no. 40:9983-9992. PNNL-SA-60634. doi:10.1021/jp803758q
• Fan P., M. Valiev, and K. Kowalski. 2008. "Large-Scale Parallel Calculations with Combined Coupled Cluster and Molecular Mechanics Formalism: Excitation Energies of Zinc-porphyrin in Aqueous Solution." Chemical Physics Letters 458, no. 1-3:205-209. PNNL-SA-58403.
• Hammond J.R., W.A. De Jong, and K. Kowalski. 2008. "Coupled-Cluster Dynamic Polarizabilities Including Triple Excitations." Journal of Chemical Physics 128. PNNL-SA-59595. doi:10.1063/1.2929840
• Kowalski K., and M. Valiev. 2008. "NonIterative Corrections to Equation-of-Motion Coupled-Cluster Excited State Energies Based on the Reduced Method of Moments of coupled cluster equation." International Journal of Quantum Chemistry 108, no. 12:2178-2190. PNNL-SA-53239. doi:10.1002/qua.21741
• Kowalski K., and M. Valiev. 2008. "The Application of High-Level Iterative Coupled-Cluster Methods to the Cytosine Molecule." Journal of Physical Chemistry A 112, no. 24:5538-5541. PNNL-SA-57526.
• Kowalski K., J.R. Hammond, W.A. De Jong, and A.J. Sadlej. 2008. "Coupled Cluster Calculations for Static and Dynamic Polarizabilities of C60." Journal of Chemical Physics 129, no. 22:226101. PNNL-SA-60838. doi:10.1063/1.3028541

2007

• Hammond J.R., K. Kowalski, and W.A. De Jong. 2007. "Dynamic Polarizabilities of Polyaromatic Hydrocarbons Using Coupled-Cluster Linear Response Theory." Journal of Chemical Physics 127. PNNL-SA-55321. doi:10.1063/1.2772853
• Hammond J.R., M. Valiev, W.A. De Jong, and K. Kowalski. 2007. "Calculations of Molecular Properties in Hybrid Coupled-Cluster and Molecular Mechanics Approach." Journal of Physical Chemistry A 111, no. 25:5492-5498. PNNL-SA-53480. doi:10.1021/jp070553x
• Kowalski K., J.R. Hammond, and W.A. De Jong. 2007. "Linear Response Coupled Cluster Singles and Doubles Approach with Modified Spectral Resolution of the Similarity Transformed Hamiltonian." Journal of Chemical Physics 127, no. 16:164105 (9). PNNL-SA-56124. doi:10.1063/1.2795708
• Tsai M.K., K. Kowalski, M. Valiev, and M. Dupuis. 2007. "Signature OH Absorption Spectrum from cluster Models of Solvation: a solvent-to-solute charge transfer state." Journal of Physical Chemistry A 111, no. 42:10478-10482. PNNL-SA-55912. doi:10.1021/jp074617f
• Valiev M., B.C. Garrett, M.K. Tsai, K. Kowalski, S.M. Kathmann, G.K. Schenter, and M. Dupuis. 2007. "Hybrid Approach for Free Energy Calculations with High-Level Methods: Application to the S(N)2 Reaction of CHCl3 and OH- in Water." Journal of Chemical Physics 127, no. 5:51102 (1-4). PNNL-SA-55381.

2006

• Dean D.J., M. Hjorth-Jensen, K. Kowalski, P. Piecuch, and M.W. Wloch. 2006. "Coupled-Cluster Theory for Nuclei." In Condensed Matter Theories, edited by John W. Clark, Robert M. Panoff, and Haochen Li. 89-97. Hauppauge, New York:Nova Publishers. PNNL-SA-43982.
• Kowalski K. 2006. "Excitation Energies Through the Locally Renormalized Equation-of-Motion Formalism: Singles and Doubles Model." Journal of Chemical Physics 125, no. 12:124101 (11 p.). PNNL-SA-50181.
• Kowalski K. 2006. "Locally Renormalized Coupled-Cluster Equations for Singly and Doubly Excited Clusters." Molecular Physics 104, no. 13-14:1989-1997. PNNL-SA-46207. doi:10.1080/00268970600668629
• Kowalski K., and M. Valiev. 2006. "Asymptotic Extrapolation Scheme for Large-Scale Calculations with Hybrid Coupled Cluster and Molecular Dynamic Simulations." Journal of Physical Chemistry A 110, no. 48:13106-13111. PNNL-SA-50543.
• Kowalski K., and M. Valiev. 2006. "Multiscale Dynamical Framework for High-Level Calculations of Finite Temperature Ground and Excited State Properties." In Journal of Physics: Conference Series ; SciDAC 2006, SCIENTIFIC DISCOVERY THROUGH ADVANCED COMPUTING, 25-29 June 2006, Denver, Colorado, USA, 46, 244-248. Philadelphia, Pennsylvania:Institute of Phyics Publishing. PNNL-SA-50655. doi:10.1088/1742-6596/46/1/035
• Kowalski K., and W.A. De Jong. 2006. "Noniterative Inclusion of the Triply and Quadruply Excited Clusters: The Locally Renormalized Perspective." Journal of Molecular Structure - Theochem 768, no. 1-3:45-52. PNNL-SA-48050.
• Song J., E. Apra, Y. Khait, M.R. Hoffmann, and K. Kowalski. 2006. "High-Level Ab-Initio Calculation on the NiO2 System." Chemical Physics Letters 428, no. 4-6:277-282. PNNL-SA-50204.
• Valiev M., and K. Kowalski. 2006. "Hybrid Coupled Cluster and Molecular Dynamics Approach: Application to the Excitation Spectrum of Cytosine in the Native DNA Environment." Journal of Chemical Physics 125, no. 21:Art. No. 211101. PNNL-SA-49559. doi:10.1063/1.2403847

2005

• Kowalski K. 2005. "Completely Renormalized EOMCCSD(T) Method Employing Independent Optimization of the Cluster Product Terms." Chemical Physics Letters 411, no. 4-6:306-310. PNNL-SA-45586. doi:10.1016/j.cplett.2005.06.024
• Kowalski K. 2005. "Implementation of the Locally Renormalized CCSD (T) Approaches for Abitrary Reference Function." Journal of Chemical Physics 123, no. 1:014102 (9 pages). PNNL-SA-44747.
• Kowalski K., S. Hirata, M.W. Wloch, P. Piecuch, and T.L. Windus. 2005. "Active-Space Coupled-Cluster Study of Electronic States of Be3." Journal of Chemical Physics 123. PNNL-SA-45585.
• Piecuch P., S. Hirata, K. Kowalski, P. Fan, and T.L. Windus. 2005. "Automated Derivation and Parallel Computer Implementation of Renormalized and Active-Space Coupled-Cluster Methods." International Journal of Quantum Chemistry 106, no. 1:79-97. PNNL-SA-47875.