TY - JOUR AB - CP2K is an open source electronic structure and molecular dynamics software package to perform atomistic simulations of solid-state, liquid, molecular, and biological systems. It is especially aimed at massively parallel and linear-scaling electronic structure methods and state-of-theart ab initio molecular dynamics simulations. Excellent performance for electronic structure calculations is achieved using novel algorithms implemented for modern high-performance computing systems. This review revisits the main capabilities of CP2K to perform efficient and accurate electronic structure simulations. The emphasis is put on density functional theory and multiple post–Hartree–Fock methods using the Gaussian and plane wave approach and its augmented all-electron extension. AU - Kühne, Thomas AU - Iannuzzi, Marcella AU - Ben, Mauro Del AU - Rybkin, Vladimir V. AU - Seewald, Patrick AU - Stein, Frederick AU - Laino, Teodoro AU - Khaliullin, Rustam Z. AU - Schütt, Ole AU - Schiffmann, Florian AU - Golze, Dorothea AU - Wilhelm, Jan AU - Chulkov, Sergey AU - Mohammad Hossein Bani-Hashemian, Mohammad Hossein Bani-Hashemian AU - Weber, Valéry AU - Borstnik, Urban AU - Taillefumier, Mathieu AU - Jakobovits, Alice Shoshana AU - Lazzaro, Alfio AU - Pabst, Hans AU - Müller, Tiziano AU - Schade, Robert AU - Guidon, Manuel AU - Andermatt, Samuel AU - Holmberg, Nico AU - Schenter, Gregory K. AU - Hehn, Anna AU - Bussy, Augustin AU - Belleflamme, Fabian AU - Tabacchi, Gloria AU - Glöß, Andreas AU - Lass, Michael AU - Bethune, Iain AU - Mundy, Christopher J. AU - Plessl, Christian AU - Watkins, Matt AU - VandeVondele, Joost AU - Krack, Matthias AU - Hutter, Jürg ID - 16277 IS - 19 JF - The Journal of Chemical Physics TI - CP2K: An electronic structure and molecular dynamics software package - Quickstep: Efficient and accurate electronic structure calculations VL - 152 ER - TY - CONF AB - Electronic structure calculations based on density-functional theory (DFT) represent a significant part of today's HPC workloads and pose high demands on high-performance computing resources. To perform these quantum-mechanical DFT calculations on complex large-scale systems, so-called linear scaling methods instead of conventional cubic scaling methods are required. In this work, we take up the idea of the submatrix method and apply it to the DFT computations in the software package CP2K. For that purpose, we transform the underlying numeric operations on distributed, large, sparse matrices into computations on local, much smaller and nearly dense matrices. This allows us to exploit the full floating-point performance of modern CPUs and to make use of dedicated accelerator hardware, where performance has been limited by memory bandwidth before. We demonstrate both functionality and performance of our implementation and show how it can be accelerated with GPUs and FPGAs. AU - Lass, Michael AU - Schade, Robert AU - Kühne, Thomas AU - Plessl, Christian ID - 16898 T2 - Proc. International Conference for High Performance Computing, Networking, Storage and Analysis (SC) TI - A Submatrix-Based Method for Approximate Matrix Function Evaluation in the Quantum Chemistry Code CP2K ER - TY - JOUR AB - In scientific computing, the acceleration of atomistic computer simulations by means of custom hardware is finding ever-growing application. A major limitation, however, is that the high efficiency in terms of performance and low power consumption entails the massive usage of low precision computing units. Here, based on the approximate computing paradigm, we present an algorithmic method to compensate for numerical inaccuracies due to low accuracy arithmetic operations rigorously, yet still obtaining exact expectation values using a properly modified Langevin-type equation. AU - Rengaraj, Varadarajan AU - Lass, Michael AU - Plessl, Christian AU - Kühne, Thomas ID - 12878 IS - 2 JF - Computation TI - Accurate Sampling with Noisy Forces from Approximate Computing VL - 8 ER - TY - JOUR AU - Ohto, Tatsuhiko AU - Dodia, Mayank AU - Xu, Jianhang AU - Imoto, Sho AU - Tang, Fujie AU - Zysk, Frederik AU - Kühne, Thomas D. AU - Shigeta, Yasuteru AU - Bonn, Mischa AU - Wu, Xifan AU - Nagata, Yuki ID - 15738 JF - The Journal of Physical Chemistry Letters SN - 1948-7185 TI - Accessing the Accuracy of Density Functional Theory through Structure and Dynamics of the Water–Air Interface VL - 10 ER - TY - JOUR AU - Azadi, Sam AU - Kühne, Thomas D. ID - 15739 JF - Physical Review B SN - 2469-9950 TI - Unconventional phase III of high-pressure solid hydrogen VL - 100 ER - TY - JOUR AU - Guc, Maxim AU - Kodalle, Tim AU - Kormath Madam Raghupathy, Ramya AU - Mirhosseini, Hossein AU - Kühne, Thomas D. AU - Becerril-Romero, Ignacio AU - Pérez-Rodríguez, Alejandro AU - Kaufmann, Christian A. AU - Izquierdo-Roca, Victor ID - 15740 JF - The Journal of Physical Chemistry C SN - 1932-7447 TI - Vibrational Properties of RbInSe2: Raman Scattering Spectroscopy and First-Principle Calculations VL - 124 ER - TY - JOUR AU - Müller, Patrick AU - Neuba, Adam AU - Flörke, Ulrich AU - Henkel, Gerald AU - Kühne, Thomas D. AU - Bauer, Matthias ID - 16320 JF - The Journal of Physical Chemistry A SN - 1089-5639 TI - Experimental and Theoretical High Energy Resolution Hard X-ray Absorption and Emission Spectroscopy on Biomimetic Cu2S2 Complexes ER - TY - THES AU - Müller, Patrick ID - 16327 TI - Experimental and theoretical (high energy resolution) X-ray absorption and emission spectroscopy / vorgelegt von Patrick Müller ; [Promotionskommission: Prof. Dr.-Ing. Hans-Joachim Warnecke, Vorsitz; Prof. Dr. Matthias Bauer, Erstgutachter; Prof. Dr. Thomas D. Kühne, Zweitgutachter; Prof. Dr. Wolf Gero Schmidt] ER - TY - JOUR AU - Kodalle, Tim AU - Kormath Madam Raghupathy, Ramya AU - Bertram, Tobias AU - Maticiuc, Natalia AU - Yetkin, Hasan A AU - Gunder, René AU - Schlatmann, Rutger AU - Kühne, Thomas D AU - Kaufmann, Christian A AU - Mirhosseini, Hossein ID - 13211 IS - 3 JF - physica status solidi (RRL)--Rapid Research Letters TI - Properties of Co-Evaporated RbInSe2 Thin Films VL - 13 ER - TY - JOUR AB - Abstract The effect of extending the O−H bond length(s) in water on the hydrogen-bonding strength has been investigated using static ab initio molecular orbital calculations. The “polar flattening” effect that causes a slight σ-hole to form on hydrogen atoms is strengthened when the bond is stretched, so that the σ-hole becomes more positive and hydrogen bonding stronger. In opposition to this electronic effect, path-integral ab initio molecular-dynamics simulations show that the nuclear quantum effect weakens the hydrogen bond in the water dimer. Thus, static electronic effects strengthen the hydrogen bond in H2O relative to D2O, whereas nuclear quantum effects weaken it. These quantum fluctuations are stronger for the water dimer than in bulk water. AU - Clark, Timothy AU - Heske, Julian Joachim AU - Kühne, Thomas ID - 13225 JF - ChemPhysChem KW - ab initio calculations KW - bond theory KW - hydrogen bonds KW - isotope effects KW - solvent effects TI - Opposing Electronic and Nuclear Quantum Effects on Hydrogen Bonds in H2O and D2O VL - 20 ER - TY - JOUR AU - Kaliannan, Naveen Kumar AU - Henao Aristizabal, Andres AU - Wiebeler, Hendrik AU - Zysk, Frederik AU - Ohto, Tatsuhiko AU - Nagata, Yuki AU - D. Kühne, Thomas ID - 13232 JF - Molecular Physics TI - Impact of intermolecular vibrational coupling effects on the sum-frequency generation spectra of the water/air interface ER - TY - JOUR AU - Müller, Patrick AU - Neuba, Adam AU - Flörke, Ulrich AU - Henkel, Gerald AU - Kühne, Thomas D. AU - Bauer, Matthias ID - 13233 IS - 16 JF - The Journal of Physical Chemistry A TI - Experimental and Theoretical High Energy Resolution Hard X-ray Absorption and Emission Spectroscopy on Biomimetic Cu2S2 Complexes VL - 123 ER - TY - JOUR AB - Thermal treatment of hexaazatriphenylene-hexacarbonitrile (HAT-CN) in the temperature range from 500 °C to 700 °C leads to precise control over the degree of condensation{,} and thus atomic construction and porosity of the resulting C2N-type materials. Depending on the condensation temperature of HAT-CN{,} nitrogen contents of more than 30 at% can be reached. In general{,} these carbons show adsorption properties which are comparable to those known for zeolites but their pore size can be adjusted over a wider range. At condensation temperatures of 525 °C and below{,} the uptake of nitrogen gas remains negligible due to size exclusion{,} but the internal pores are large and polarizing enough that CO2 can still adsorb on part of the internal surface. This leads to surprisingly high CO2 adsorption capacities and isosteric heat of adsorption of up to 52 kJ mol−1. Theoretical calculations show that this high binding enthalpy arises from collective stabilization effects from the nitrogen atoms in the C2N layers surrounding the carbon atom in the CO2 molecule and from the electron acceptor properties of the carbon atoms from C2N which are in close proximity to the oxygen atoms in CO2. A true CO2 molecular sieving effect is achieved for the first time in such a metal-free organic material with zeolite-like properties{,} showing an IAST CO2/N2 selectivity of up to 121 at 298 K and a N2/CO2 ratio of 90/10 without notable changes in the CO2 adsorption properities over 80 cycles. AU - Walczak, Ralf AU - Savateev, Aleksandr AU - Heske, Julian Joachim AU - Tarakina, Nadezda V. AU - Sahoo, Sudhir AU - Epping, Jan D. AU - Kühne, Thomas AU - Kurpil, Bogdan AU - Antonietti, Markus AU - Oschatz, Martin ID - 13236 JF - Sustainable Energy Fuels TI - Controlling the strength of interaction between carbon dioxide and nitrogen-rich carbon materials by molecular design ER - TY - JOUR AU - Elgabarty, Hossam AU - Kaliannan, Naveen Kumar AU - Kühne, Thomas D. ID - 13237 JF - Scientific Reports TI - Enhancement of the asymmetry in the hydrogen bond network of liquid water by an ultrafast electric field pulse VL - 9 ER - TY - JOUR AB - The behavior of alkali atom point defects in polycrystalline CuInSe2 is studied. In this work, three grain boundary models, one coherent twin boundary and two twin boundaries with dislocation cores, are considered. Total energy calculations show that all alkali metals tend to segregate at the grain boundaries. In addition, the segregation of alkali atoms is more pronounced at the grain boundaries with the dislocation cores. The diffusion of alkali metals along and near grain boundaries is studied as well. The results show that the diffusion of alkali atoms in the grain boundary models is faster than within the bulk. In addition, the ion exchange between Na and Rb atoms at the grain boundaries leads to the Rb enrichment at the grain boundaries and the increase of the Na concentration in the bulk. While the effects of Na and Rb point defects on the electronic structure of the grain boundary with the anion-core dislocation are similar, Rb atoms passivate the grain boundary with the cation-core dislocation more effectively than Na. This can explain the further improvement of the solar cell performance after the RbF-postdeposition treatment. AU - Chugh, Manjusha AU - Kühne, Thomas D. AU - Mirhosseini, Hossein ID - 13230 IS - 16 JF - ACS Applied Materials & Interfaces TI - Diffusion of Alkali Metals in Polycrystalline CuInSe2 and Their Role in the Passivation of Grain Boundaries VL - 11 ER - TY - JOUR AB - We address the general mathematical problem of computing the inverse p-th root of a given matrix in an efficient way. A new method to construct iteration functions that allow calculating arbitrary p-th roots and their inverses of symmetric positive definite matrices is presented. We show that the order of convergence is at least quadratic and that adaptively adjusting a parameter q always leads to an even faster convergence. In this way, a better performance than with previously known iteration schemes is achieved. The efficiency of the iterative functions is demonstrated for various matrices with different densities, condition numbers and spectral radii. AU - Richters, Dorothee AU - Lass, Michael AU - Walther, Andrea AU - Plessl, Christian AU - Kühne, Thomas ID - 21 IS - 2 JF - Communications in Computational Physics TI - A General Algorithm to Calculate the Inverse Principal p-th Root of Symmetric Positive Definite Matrices VL - 25 ER - TY - JOUR AB - Approximate computing has shown to provide new ways to improve performance and power consumption of error-resilient applications. While many of these applications can be found in image processing, data classification or machine learning, we demonstrate its suitability to a problem from scientific computing. Utilizing the self-correcting behavior of iterative algorithms, we show that approximate computing can be applied to the calculation of inverse matrix p-th roots which are required in many applications in scientific computing. Results show great opportunities to reduce the computational effort and bandwidth required for the execution of the discussed algorithm, especially when targeting special accelerator hardware. AU - Lass, Michael AU - Kühne, Thomas AU - Plessl, Christian ID - 20 IS - 2 JF - Embedded Systems Letters SN - 1943-0663 TI - Using Approximate Computing for the Calculation of Inverse Matrix p-th Roots VL - 10 ER - TY - JOUR AB - We performed ab initio calculations to study oxygen and hydrogen point defects in the CuInSe2 (CISe) solar-cell material. We found that H interstitial defects (when one H atom is surrounded by four Se atoms) and HCu (when a H atom is replacing a Cu atom) are the most stable defects. Whereas these H substitutional defects remain neutral, H interstitial defects act as donor defects and are detrimental to the cell performance. The incorporation of H2 into the CISe lattice, on the other hand, is harmless to the p-type conductivity. Oxygen atoms tend to either substitute Se atoms in the CISe lattice or form interstitial defects, though the formation of substitutional defects is more favorable. All oxygen point defects have high formation energies, which results in a low concentration of these defects in CISe. However, the presence of oxygen in the system leads to the formation of secondary phases such as In2O3 and InCuO2. In addition to the point defects, we studied the adsorption of H2O molecules on a defect-free surface and a surface with a (2VCu + InCu) defect using the ab initio thermodynamics technique. Our results indicate that the dissociative water adsorption on the CISe surface is energetically unfavorable. Furthermore, in order to obtain a water-free surface, the surface with defects has to be calcined at a higher temperature compared to the defect-free surface. AU - Sahoo, Sudhir AU - Kormath Madam Raghupathy, Ramya AU - Kühne, Thomas AU - Mirhosseini, Hossein ID - 13209 IS - 37 JF - J. Phys. Chem. C TI - Theoretical Investigation of Interaction of CuInSe2 Absorber Material with Oxygen, Hydrogen, and Water VL - 122 ER - TY - JOUR AB - In this work, we investigated ternary chalcogenide semiconductors to identify promising p-type transparent conducting materials (TCMs). High-throughput calculations were employed to find the compounds that satisfies our screening criteria. Our screening strategy was based on the size of band gaps, the values of hole effective masses, and p-type dopability. Our search led to the identification of seven promising compounds (IrSbS, Ba2GeSe4, Ba2SiSe4, Ba(BSe3)2, VCu3S4, NbCu3Se4, and CuBS2) as potential TCM candidates. In addition, branch point energy and optical absorption spectra calculations support our findings. Our results open a new direction for the design and development of p-type TCMs. AU - Kormath Madam Raghupathy, Ramya AU - Wiebeler, Hendrik AU - Kühne, Thomas AU - Felser, Claudia AU - Mirhosseini, Hossein ID - 13210 IS - 19 JF - Chemistry of Materials TI - Database screening of ternary chalcogenides for p-type transparent conductors VL - 30 ER - TY - JOUR AU - Müller, Patrick AU - Karhan, Kristof AU - Krack, Matthias AU - Gerstmann, Uwe AU - Schmidt, Wolf Gero AU - Bauer, Matthias AU - Kühne, Thomas D. ID - 13405 JF - Journal of Computational Chemistry SN - 0192-8651 TI - Impact of finite-temperature and condensed-phase effects on theoretical X-ray absorption spectra of transition metal complexes ER -