arXiv subjects

Sriram Krishnamoorthy

Publications and source records attributed to Sriram Krishnamoorthy.

At least 37 records · Page 2Linked to original sources

arXiv2023

Over 6 $μ$m thick MOCVD-grown Low-Background Carrier Density (10$^{15}$ cm$^{-3}$) High-Mobility (010) $β$-Ga$_2$O$_3$ Drift Layers

This work reports high carrier mobilities and growth rates, simultaneously in low unintentionally-doped UID (10$^{15}$ cm$^{-3}$) MOCVD-grown thick $β$-Ga$_2$O$_3$ epitaxial drift layers, with thicknesses reaching up to 6.3 $μ$m, using triethylgallium (TEGa) as a precursor. Record high room temperature Hall mobilities of 187-190 cm$^2$/Vs were measured for background carrier density values of 2.4 - 3.5$\times$10$^{15}$ cm$^{-3}$ grown at a rate of 2.2 $μ$m/hr. A controlled background carrier density scaling from 3.3$\times$10$^{16}$ cm$^{-3}$ to 2.4$\times$10$^{15}$ cm$^{-3}$ is demonstrated, without the use of intentional dopant gases such as silane, by controlling the growth rate and O$_2$/TEGa ratio. Films show smooth surface morphologies of 0.8-3.8 nm RMS roughness for film thicknesses of 1.24 - 6.3$μ$m. Vertical Ni Schottky barrier diodes (SBDs) fabricated on UID MOCVD material were compared with those fabricated on hydride vapor phase epitaxy (HVPE) material, revealing superior material and device characteristics. MOCVD SBDs on a 6.3 $μ$m thick epitaxial layer show a uniform charge vs. depth profile of $\sim$2.4$\times$10$^{15}$ cm$^{-3}$, an estimated $μ$$_{drift}$ of 132 cm$^2$/Vs, a breakdown voltage (V$_{BR}$) close to 1.2 kV and a surface parallel plane field of 2.05MV/cm without any electric field management - setting record-high parameters for any MOCVD-grown $β$-Ga$_2$O$_3$ vertical diode to date.

physics.app-ph↗

arXiv2023

TAMM: Tensor Algebra for Many-body Methods

Tensor contraction operations in computational chemistry consume significant fractions of computing time on large-scale computing platforms. The widespread use of tensor contractions between large multi-dimensional tensors in describing electronic structure theory has motivated the development of multiple tensor algebra frameworks targeting heterogeneous computing platforms. In this paper, we present Tensor Algebra for Many-body Methods (TAMM), a framework for productive and performance-portable development of scalable computational chemistry methods. The TAMM framework decouples the specification of the computation and the execution of these operations on available high-performance computing systems. With this design choice, the scientific application developers (domain scientists) can focus on the algorithmic requirements using the tensor algebra interface provided by TAMM whereas high-performance computing developers can focus on various optimizations on the underlying constructs such as efficient data distribution, optimized scheduling algorithms, efficient use of intra-node resources (e.g., GPUs). The modular structure of TAMM allows it to be extended to support different hardware architectures and incorporate new algorithmic advances. We describe the TAMM framework and our approach to sustainable development of tensor contraction-based methods in computational chemistry applications. We present case studies that highlight the ease of use as well as the performance and productivity gains compared to other implementations.

cs.DC↗

arXiv2023

Ultra-Wide Bandgap Ga$_2$O$_3$-on-SiC MOSFETs

Ulta-wide bandgap semiconductors based on $β$-Ga$_2$O$_3$ offer the potential to achieve higher power switching performance, efficiency, and lower manufacturing cost than today's wide bandgap power semiconductors. However, the most critical challenge to the commercialization of Ga$_2$O$_3$ electronics is overheating, which impacts the device's performance and reliability. We fabricated a Ga$_2$O$_3$/4H-SiC composite wafer using a fusion-bonding method. A low temperature ($\le$ 600 $^{\circ}$C) epitaxy and device processing approach based on low-temperature (LT) metalorganic vapor phase epitaxy is developed to grow a Ga$_2$O$_3$ epitaxial channel layer on the composite wafer and subsequently fabricate into Ga$_2$O$_3$ power MOSFETs. This LT approach is essential to preserve the structural integrity of the composite wafer. These LT-grown epitaxial Ga$_2$O$_3$ MOSFETs deliver high thermal performance (56% reduction in channel temperature), high voltage blocking capabilities up to 2.45 kV, and power figures of merit of $\sim$ 300 MW/cm$^2$, which is a record high for any heterogeneously integrated Ga$_2$O$_3$ devices reported to date. This work is the first realization of multi-kilovolt homoepitaxial Ga$_2$O$_3$ power MOSFETs fabricated on a composite substrate with high heat transfer performance which delivers state-of-the-art power density values while running much cooler than those on native substrates. Thermal characterization and modeling results reveal that a Ga$_2$O$_3$/diamond composite wafer with a reduced Ga$_2$O$_3$ thickness ($\sim$ 1 $μ$m) and thinner bonding interlayer ($<$ 10 nm) can reduce the device thermal impedance to a level lower than today's GaN-on-SiC power switches.

cond-mat.mtrl-sci↗

arXiv2023

Enhancing the Electron Mobility in Si-doped (010) $β$-Ga$_2$O$_3$ films with Low-Temperature Buffer Layers

We demonstrate a new substrate cleaning and buffer growth scheme in $β$-Ga$_2$O$_3$ epitaxial thin films using metalorganic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 $^\circ$C) undoped Ga$_2$O$_3$ buffer is grown followed by transition layers to a high-temperature (HT, 810 $^\circ$C) Si-doped Ga$_2$O$_3$ channel layers without growth interruption. The (010) Ga$_2$O$_3$ Fe-doped substrate cleaning uses solvent cleaning followed by an additional HF (49% in water) treatment for 30 mins before the epilayer growth. This step is shown to compensate the parasitic Si channel at the epilayer-substrate interface that originates from the substrate polishing process or contamination from the ambient. SIMS analysis shows the Si peak atomic density at the substrate interface is several times lower than the Fe atomic density in the substrate - indicating full compensation. The elimination of the parasitic electron channel at the epi-substrate interface was also verified by electrical (capacitance-voltage profiling) measurements. In the LT-grown buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp with a decay rate of $\sim$ 9 nm$/$dec. These channels show record high electron mobility in the range of 196 - 85 cm$^2$/Vs in unintentionally doped and Si-doped films in the doping range of 2$\times$10$^{16}$ to 1$\times$10$^{20}$ cm$^{-3}$. Si delta-doped channels were also grown utilizing this substrate cleaning and the hybrid LT-buffers. Record high electron Hall mobility of 110 cm$^2$/Vs was measured for sheet charge density of 9.2$\times$10$^{12}$ cm$^{-2}$. This substrate cleaning combined with the LT-buffer scheme shows the potential of designing Si-doped $β$-Ga$_2$O$_3$ channels with exceptional transport properties for high performance gallium oxide-based electron devices.

cond-mat.mtrl-sci↗

arXiv2022

Low Resistance Ohmic Contact On Epitaxial MOVPE-grown $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ Films

We report on the realization of record low resistance Ohmic contacts to MOVPE-grown heavily Si-doped $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ epitaxial films. Transfer length measurement (TLM) patterns were fabricated on the heavily Si-doped homoepitaxial $β$-Ga$_2$O$_3$ films with electron concentration (n) ranging from 1.77 to 3.23e20 cm^-3. Record low specific contact resistance and total contact resistance (Rc) of 1.62e-7 Ohm.cm^2 and 0.023 Ohm.mm were realized for $β$-Ga$_2$O$_3$: Si films with n > 3e20 cm^-3. TLM structures were also fabricated on heavily Si doped coherently strained $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ (x=12%, 17% and 22%) films. The film with 12% Al composition (n=1.23e20 cm^-3) showed \r{ho}c of 5.85e-6 Ohm.cm^2, but it increased to 2.19e-4 Ohm.cm^2 for a layer with a 22% Al composition. Annealing the samples post metal deposition has generally led to a decrease in contact resistance, but for high Al content $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$, the contact resistance did not change significantly after the annealing process. The low contact resistance values measured in this work are very promising for the fabrication of high frequency power devices.

cond-mat.mtrl-sci↗

arXiv2022

High-Mobility Tri-Gate $β$-Ga$_2$O$_3$ MESFETs with a Power Figure of Merit over 0.9 GW/cm$^2$

In this letter, fin-shape tri-gate $β$-Ga$_{2}$O$_{3}$ lateral MESFETs are demonstrated with a high power figure of merit of 0.95 GW/cm$^{2}$ - a record high for any $β$-Ga$_{2}$O$_{3}$ transistor to date. A low-temperature undoped buffer-channel stack design is developed which demonstrates record high Hall and drift electron mobilities in doped $β$-Ga$_{2}$O$_{3}$ channels allowing for low ON resistances R$_{ON}$ in $β$-Ga$_{2}$O$_{3}$ MESFETs. Fin-widths (W$_{fin}$) were 1.2-1.5 $μ$m and there were 25 fins (N$_{fin}$) per device with a trench depth of $\sim$1$μ$m. A $β$-Ga$_2$O$_3$ MESFET with a source-drain length of 6.4 $μ$m exhibits a high ON current (187 mA/mm), low R$_{ON}$ (20.5 $Ω$.mm) and a high average breakdown field (4.2 MV/cm). All devices show very low reverse leakage until catastrophic breakdown for breakdown voltages scaled from 1.1kV to $\sim$3kV. This work demonstrates the potential of channel engineering in improving $β$-Ga$_{2}$O$_{3}$ device performance toward lower conduction losses for low-to-medium voltage applications.

physics.app-ph↗

arXiv2022

Optimized Quantum Phase Estimation for Simulating Electronic States in Various Energy Regimes

While quantum algorithms for simulation exhibit better asymptotic scaling than their classical counterparts, they currently cannot be implemented on real-world devices. Instead, chemists and computer scientists rely on costly classical simulations of these quantum algorithms. In particular, the quantum phase estimation (QPE) algorithm is among several approaches that have attracted much attention in recent years for its genuine quantum character. However, it is memory-intensive to simulate and intractable for moderate system sizes. This paper discusses the performance and applicability of QPESIM, a new simulation of the QPE algorithm designed to take advantage of modest computational resources. In particular, we demonstrate the versatility of QPESIM in simulating various electronic states by examining the ground and core-level states of H$_2$O. For these states, we also discuss the effect of the active-space size on the quality of the calculated energies. For the high-energy core-level states, we demonstrate that new QPE simulations for active spaces defined by 15 active orbitals significantly reduce the errors in core-level excitation energies compared to earlier QPE simulations using smaller active spaces.

quant-ph↗

arXiv2022

Efficient Hierarchical State Vector Simulation of Quantum Circuits via Acyclic Graph Partitioning

Early but promising results in quantum computing have been enabled by the concurrent development of quantum algorithms, devices, and materials. Classical simulation of quantum programs has enabled the design and analysis of algorithms and implementation strategies targeting current and anticipated quantum device architectures. In this paper, we present a graph-based approach to achieve efficient quantum circuit simulation. Our approach involves partitioning the graph representation of a given quantum circuit into acyclic sub-graphs/circuits that exhibit better data locality. Simulation of each sub-circuit is organized hierarchically, with the iterative construction and simulation of smaller state vectors, improving overall performance. Also, this partitioning reduces the number of passes through data, improving the total computation time. We present three partitioning strategies and observe that acyclic graph partitioning typically results in the best time-to-solution. In contrast, other strategies reduce the partitioning time at the expense of potentially increased simulation times. Experimental evaluation demonstrates the effectiveness of our approach.

quant-ph↗

arXiv2022

QASMBench: A Low-level QASM Benchmark Suite for NISQ Evaluation and Simulation

The rapid development of quantum computing (QC) in the NISQ era urgently demands a low-level benchmark suite and insightful evaluation metrics for characterizing the properties of prototype NISQ devices, the efficiency of QC programming compilers, schedulers and assemblers, and the capability of quantum system simulators in a classical computer. In this work, we fill this gap by proposing a low-level, easy-to-use benchmark suite called QASMBench based on the OpenQASM assembly representation. It consolidates commonly used quantum routines and kernels from a variety of domains including chemistry, simulation, linear algebra, searching, optimization, arithmetic, machine learning, fault tolerance, cryptography, etc., trading-off between generality and usability. To analyze these kernels in terms of NISQ device execution, in addition to circuit width and depth, we propose four circuit metrics including gate density, retention lifespan, measurement density, and entanglement variance, to extract more insights about the execution efficiency, the susceptibility to NISQ error, and the potential gain from machine-specific optimizations. Applications in QASMBench can be launched and verified on several NISQ platforms, including IBM-Q, Rigetti, IonQ and Quantinuum. For evaluation, we measure the execution fidelity of a subset of QASMBench applications on 12 IBM-Q machines through density matrix state tomography, which comprises 25K circuit evaluations. We also compare the fidelity of executions among the IBM-Q machines, the IonQ QPU and the Rigetti Aspen M-1 system. QASMBench is released at: http://github.com/pnnl/QASMBench.

quant-ph↗

arXiv2022

Alloyed B-(AlxGa1-x)2O3 bulk Czochralski single B-(Al0.1Ga0.9)2O3 and polycrystals B-(Al0.33Ga0.66)2O3, B-(Al0.5Ga0.5)2O3), and property trends

In this work, bulk Czochralski-grown single crystals of 10 mol. % Al2O3 alloyed B-Ga2O3 - monoclinic 10% AGO or B-(Al0.1Ga0.9)2O3 - are obtained, which show +0.20 eV increase in the bandgap compared with unintentionally doped B-Ga2O3. Further, growths of 33% AGO - B-(Al0.33Ga0.67)2O3 - and 50% AGO - B-(Al0.5Ga0.5)2O3 or B-AlGaO3 - produce polycrystalline single-phase monoclinic material (B-AGO). All three compositions are investigated by x-ray diffraction, Raman spectroscopy, optical absorption, and 27Al nuclear magnetic resonance (NMR). By investigating single phase B-AGO over a large range of Al2O3 concentrations (10 - 50 mol. %), broad trends in the lattice parameter, vibrational modes, optical bandgap, and crystallographic site preference are determined. All lattice parameters show a linear trend with Al incorporation. According to NMR, aluminum incorporates on both crystallographic sites of B-Ga2O3, with a slight preference for the octahedral (GaII) site, which becomes more disordered with increasing Al. Single crystals of 10% AGO were also characterized by x-ray rocking curve, transmission electron microscopy, purity (glow discharge mass spectroscopy and x-ray fluorescence), optical transmission (200 nm - 20 um wavelengths), and resistivity. These measurements suggest that electrical compensation by impurity acceptor doping is not the likely explanation for high resistivity, but rather the shift of a hydrogen level from a shallow donor to a deep acceptor due to Al alloying. .. Cont. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Journal of Applied Physics 131 155702.

cond-mat.mtrl-sci↗

arXiv2022

4.4 kV $β$-Ga$_2$O$_3$ Power MESFETs with Lateral Figure of Merit exceeding 100 MW/cm$^2$

Field-plated (FP) depletion-mode MOVPE-grown $β$-Ga$_2$O$_3$ lateral MESFETs are realized with superior reverse breakdown voltages and ON currents. A sandwiched SiN$_x$ dielectric field plate design was utilized that prevents etching-related damage in the active region and a deep mesa-etching was used to reduce reverse leakage. The device with L$_{GD}$ = 34.5 $μ$m exhibits an ON current (I$_{DMAX}$) of 56 mA/mm, a high I$_{ON}$/I$_{OFF}$ ratio $>$ 10$^8$ and a very low reverse leakage until catastrophic breakdown at $\sim$ 4.4kV. The highest measurable V$_{BR}$ recorded was 4.57 kV (L$_{GD}$ = 44.5 $μ$m). An LFOM of 132 MW/cm$^2$ was calculated for a V$_{BR}$ of $\sim$ 4.4 kV. The reported results are the first $>$ 4kV-class Ga$_2$O$_3$ transistors to surpass the theoretical FOM of Silicon. These are also the highest I$_{DMAX}$ and lowest R$_{ON}$ values achieved simultaneously for any $β$-Ga$_2$O$_3$ device with V$_{BR}$ $>$ 4kV to date. This work highlights that high breakdown voltages (V$_{BR}$), high lateral figure of merit (LFOM) and high ON currents can be achieved simultaneously in $β$-Ga$_2$O$_3$ lateral transistors.

physics.app-ph↗

arXiv2021

Characterizing Impacts of Storage Faults on HPC Applications: A Methodology and Insights

In recent years, the increasing complexity in scientific simulations and emerging demands for training heavy artificial intelligence models require massive and fast data accesses, which urges high-performance computing (HPC) platforms to equip with more advanced storage infrastructures such as solid-state disks (SSDs). While SSDs offer high-performance I/O, the reliability challenges faced by the HPC applications under the SSD-related failures remains unclear, in particular for failures resulting in data corruptions. The goal of this paper is to understand the impact of SSD-related faults on the behaviors of complex HPC applications. To this end, we propose FFIS, a FUSE-based fault injection framework that systematically introduces storage faults into the application layer to model the errors originated from SSDs. FFIS is able to plant different I/O related faults into the data returned from underlying file systems, which enables the investigation on the error resilience characteristics of the scientific file format. We demonstrate the use of FFIS with three representative real HPC applications, showing how each application reacts to the data corruptions, and provide insights on the error resilience of the widely adopted HDF5 file format for the HPC applications.

cs.DC↗

arXiv2021

130 mA/mm $β$-Ga$_2$O$_3$ MESFET with Low-Temperature MOVPE-Regrown Ohmic Contacts

We report on the demonstration of metalorganic vapor phase epitaxy-regrown (MOVPE) ohmic contacts in an all MOVPE-grown $β$-Ga$_2$O$_3$ metal-semiconductor field effect transistor (MESFET). The low-temperature (600$^{\circ}$C) heavy (n$^{+}$) Si-doped regrown layers exhibit extremely high conductivity with sheet resistance of 73 $Ω$/$\square$ and record low metal/n$^{+}$-Ga$_2$O$_3$ contact resistance of 80 m$Ω$.mm and specific contact resistivity of 8.3$\times$10$^{-7}$ $Ω$.cm$^{2}$ were achieved. The fabricated MESFETs exhibit a maximum drain-to-source current of 130 mA/mm, a high I$_{ON}$/I$_{OFF}$ of $>$10$^{10}$ with a high power FOM of 25 MW/cm$^{2}$ were achieved without any field plates. Nanoparticle-assisted Raman thermometry, thermal modeling, and infrared thermography were performed to assess the device self-heating under the high current and power conditions. This demonstration shows the promise of MOVPE technique for the realization of high-performance lateral $β$-Ga$_2$O$_3$ devices and also highlights the need for device-level thermal management.

physics.app-ph↗

arXiv2021

Multi-kV class $β$-Ga$_2$O$_3$ MESFETs with a Lateral Figure of Merit up to 355 MW/cm$^2$

We demonstrate over 3 kV gate-pad-connected field plated (GPFP) $β$-Ga$_2$O$_3$ lateral MESFETs with high lateral figure of merit (LFOM) using metalorganic vapor phase epitaxy (MOVPE) grown channel layers and regrown ohmic contact layers. Using an improved low-temperature MOVPE selective area epitaxy process, we show that a total contact resistance to the channel as low as 1.4 $Ω$.mm can be achieved.The GPFP design adopted here using PECVD (plasma-enhanced chemical vapor deposition) deposited SiN$_x$ dielectric and SiN$_x$/SiO$_2$ wrap-around passivation exhibits up to ~14% improved R$_{ON}$, up to ~70% improved breakdown voltage (V$_{BR}$ = V$_{DS}$ - V$_{GS}$) resulting in up to $\sim$3$\times$ higher LFOM compared to non-FP $β$-Ga$_2$O$_3$ lateral MESFETs. The V$_{BR}$ (~2.5 kV) and LFOM (355 MW/cm$^2$) measured simultaneously in our GPFP $β$-Ga$_2$O$_3$ lateral MESFET (with L$_{GD}$ = 10 $μ$m) is the highest value achieved in any depletion-mode $β$-Ga$_2$O$_3$ lateral device.

physics.app-ph↗

arXiv2021

Spalling-induced liftoff and transfer of electronic films using a van der Waals release layer

Heterogeneous integration strategies are increasingly being employed to achieve more compact and capable electronics systems for multiple applications including space, electric vehicles, and wearable and medical devices. To enable new integration strategies, the growth and transfer of thin electronic films and devices, including III-nitrides, metal oxides, and two-dimensional (2D) materials, using 2D boron nitride (BN)-on-sapphire templates is demonstrated. The van der Waals BN layer, in this case, acts as a preferred mechanical release layer for precise separation at the substrate-film interface and leaves a smooth surface suitable for van der Waals bonding. A tensilely-stressed Ni layer sputtered on top of the film induces controlled spalling fracture which propagates at the BN/sapphire interface. By incorporating controlled spalling, the process yield and sensitivity is greatly improved, owed to the greater fracture energy provided by the stressed metal layer relative to a soft tape or rubber stamp. With stress playing a critical role in this process, the influence of residual stress on detrimental cracking and bowing is investigated. Additionally, a selected area lift-off technique is developed which allows for isolation and transfer of individual devices while maximizing wafer area use and minimizing extra alignment steps in the integration process.

physics.app-ph↗

arXiv2021

High Permittivity Dielectric Field-Plated Vertical (001) $β$-Ga$_2$O$_3$ Schottky Barrier Diode with Surface Breakdown Electric Field of 5.45 MV/cm and BFOM of $>$ 1 GW/cm$^{2}$

This paper presents vertical (001) oriented $β$-Ga$_2$O$_3$ field plated (FP) Schottky barrier diode (SBD) with a novel extreme permittivity dielectric field oxide. A thin drift layer of 1.7 $μm$ was used to enable a punch-through (PT) field profile and very low differential specific on-resistance (R$_{on-sp}$) of 0.32 m$Ω$-cm$^{2}$. The extreme permittivity field plate oxide facilitated the lateral spread of the electric field profile beyond the field plate edge and enabled a breakdown voltage ($V_{br}$) of 687 V. The edge termination efficiency increases from 13.5 $\%$ for non-field plated structure to 63 $\%$ for high permittivity field plate structure. The surface breakdown electric field was extracted to be 5.45 MV/cm at the center of the anode region using TCAD simulations. The high permittivity field plated SBD demonstrated a record high Baliga figure of merit (BFOM) of 1.47 GW/cm$^{2}$ showing the potential of Ga$_2$O$_3$ power devices for multi-kilovolt class applications.

cond-mat.mtrl-sci↗

arXiv2021

In-situ dielectric Al2O3/\b{eta}-Ga2O3 Interfaces Grown Using Metal-organic Chemical Vapor Deposition

High-quality dielectric-semiconductor interfaces are critical for reliable high-performance transistors. We report the in-situ metalorganic chemical vapor deposition (MOCVD) of Al$_2$O$_3$ on $β$-Ga$_2$O$_3$ as a potentially better alternative to the most commonly used atomic layer deposition (ALD). The growth of Al$_2$O$_3$ is performed in the same reactor as Ga$_2$O$_3$ using trimethylaluminum and O$_2$ as precursors without breaking the vacuum at a growth temperature of 600 $^0$C. The fast and slow near interface traps at the Al$_2$O$_3$/ $β$-Ga$_2$O$_3$ interface are identified and quantified using stressed capacitance-voltage (CV) measurements on metal oxide semiconductor capacitor (MOSCAP) structures. The density of shallow and deep level initially filled traps (D$_{it}$) are measured using ultra-violet (UV) assisted CV technique. The average D$_{it}$ for the MOSCAP is determined to be 7.8 $\times$ 10$^{11}$ cm$^{-2}$eV$^{-1}$. The conduction band offset of the Al$_2$O$_3$/ Ga$_2$O$_3$ interface is also determined from CV measurements and found out to be 1.7 eV which is in close agreement with the existing literature reports of ALD Al$_2$O$_3$/ Ga$_2$O$_3$ interface. The current-voltage characteristics are also analyzed and the average breakdown field is extracted to be approximately 5.8 MV/cm. This in-situ Al$_2$O$_3$ dielectric on $β$-Ga$_2$O$_3$ with improved dielectric properties can enable Ga$_2$O$_3$-based high performance devices.

cond-mat.mtrl-sci↗

arXiv2021

GFCCLib: Scalable and Efficient Coupled-Cluster Green's Function Library for Accurately Tackling Many Body Electronic Structure Problems

Coupled cluster Green's function (GFCC) calculation has drawn much attention in the recent years for targeting the molecular and material electronic structure problems from a many body perspective in a systematically improvable way. However, GFCC calculations on scientific computing clusters usually suffer from expensive higher dimensional tensor contractions in the complex space, expensive interprocess communication, and severe load imbalance, which limits it's routine use for tackling electronic structure problems. Here we present a numerical library prototype that is specifically designed for large scale GFCC calculations. The design of the library is focused on a systematically optimal computing strategy to improve its scalability and efficiency. The performance of the library is demonstrated by the relevant profiling analysis of running GFCC calculations on remote giant computing clusters. The capability of the library is highlighted by computing a wide near valence band of a fullerene C60 molecule for the first time at the GFCCSD level that shows excellent agreement with the experimental spectrum.

physics.chem-ph↗