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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on VPt by Materials Project

PtV is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. V2+ is bonded to eight equivalent Pt2- atoms to form distorted VPt8 hexagonal bipyramids that share corners with sixteen equivalent PtV8Pt4 cuboctahedra, corners with eight equivalent VPt8 hexagonal bipyramids, edges with eight equivalent PtV8Pt4 cuboctahedra, edges with twelve equivalent VPt8 hexagonal bipyramids, and faces with six equivalent VPt8 hexagonal bipyramids. All V–Pt bond lengths are 2.74 Å. Pt2- is bonded to eight equivalent V2+ and four equivalent Pt2- atoms to form distorted PtV8Pt4 cuboctahedra that share corners with twelve equivalent PtV8Pt4 cuboctahedra, corners with sixteen equivalent VPt8 hexagonal bipyramids, edges with eight equivalent PtV8Pt4 cuboctahedra, edges with eight equivalent VPt8 hexagonal bipyramids, and faces with ten equivalent PtV8Pt4 cuboctahedra. All Pt–Pt bond lengths are 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VPt by Materials Project

PtV is beta-prime cadmium gold structured and crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. V2+ is bonded in a 8-coordinate geometry to eight equivalent Pt2- atoms. There are a spread of V–Pt bond distances ranging from 2.68–2.81 Å. Pt2- is bonded to eight equivalent V2+ and four equivalent Pt2- atoms to form a mixture of distorted corner, edge, and face-sharing PtV8Pt4 cuboctahedra. There are two shorter (2.71 Å) and two longer (2.81 Å) Pt–Pt bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VPt by Materials Project

PtV crystallizes in the trigonal R-3m space group. The structure is three-dimensional. V2+ is bonded in a distorted hexagonal planar geometry to six equivalent Pt2- atoms. All V–Pt bond lengths are 2.74 Å. Pt2- is bonded to six equivalent V2+ and six equivalent Pt2- atoms to form a mixture of distorted edge, face, and corner-sharing PtV6Pt6 cuboctahedra. All Pt–Pt bond lengths are 2.74 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Visual Instance-aware Prompt Tuning

Visual Prompt Tuning (VPT) has emerged as a parameter-efficient fine-tuning paradigm for vision transformers, with conventional approaches utilizing dataset-level prompts that remain the same across all input instances. We observe that this strategy results in sub-optimal performance due to high variance in downstream datasets. To address this challenge, we propose Visual Instance-aware Prompt Tuning (ViaPT), which generates instance-aware prompts based on each individual input and fuses them with dataset-level prompts, leveraging Principal Component Analysis (PCA) to retain important prompting information. Moreover, we reveal that VPT-Deep and VPT-Shallow represent two corner cases based on a conceptual understanding, in which they fail to effectively capture instance-specific information, while random dimension reduction on prompts only yields performance between the two extremes. Instead, ViaPT overcomes these limitations by balancing dataset-level and instance-level knowledge, while reducing the amount of learnable parameters compared to VPT-Deep. Extensive experiments across 34 diverse datasets demonstrate that our method consistently outperforms state-of-the-art baselines, establishing a new paradigm for analyzing and optimizing visual prompts for vision transformers.

Xiao, Xi [ORNL] (ORCID:0009000009316982)↗
DOE OSTI2022

Thermal Pressure in the Thermal Equation of State for Solid and a Proposed Substitute

Abstract The thermal equation of state (TEOS) for solids is a mathematic model among pressure, temperature and density, and is essential for geophysical, geochemical, and other high pressure–temperature (high P–T) researches. However, in the last few decades, there has been a growing concern about the accuracy of the pressure scales of the calibrants, and efforts have been made to improve it by either introducing a reference standard or building new thermal pressure models. The existing thermal equation of state, P ( V , T ) = P ( V , T 0 ) + P th ( V , T ), consists of an isothermal compression and an isochoric heating, while the thermal pressure is the pressure change in the isochoric heating. In this paper, we demonstrate that, for solids in a soft pressure medium in a diamond anvil cell, the thermal pressure can neither be determined from a single heating process, nor from the thermal pressure of its calibrant. To avoid the thermal pressure, we propose to replace the thermal pressure with a well-known thermal expansion model, and integrate it with the isothermal compression model to yields a Birch–Murnaghan-expansion TEOS model, called VPT TEOS. The predicted pressure of MgO and Au at ambient pressure from Birch–Murnaghan-expansion VPT TEOS model matches the experimental pressure of zero (0) GPa very well, while the pressure prediction from the approximated Anderson PVT TEOS exhibit a big deviation and a wrong trend.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

A Flexible Forwarding Scheme to Improve Latency-Bound Irregular P2P Communication in MPI

We propose an algorithm to efficiently perform latency-bound communication scenarios that consist of many small messages. In these parallel scenarios, processes typically pass around a lot of small-sized messages of a few KBs of size. Performing communication operations with P2P MPI routines or collective MPI routines (including neighborhood collectives) in such scenarios may not always yield the optimal results and may not resolve the latency bottleneck. To this end, we develop a regular structure called virtual process topology (VPT) on which the messages can be communicated in a structured and controlled manner. Using parameters of this topology, one can tune the rate of aggression in tackling the latency costs. We demonstrate that our communication algorithm is preferable to MPI P2P and collective routines for latency-bound communication and it can easily be adapted only by replacing calls to MPI routines in a parallel application. We show how to adapt existing topology-aware mapping heuristics to address the volume overhead due to communicating messages on the VPT. Moreover, we propose a novel swap-based mapping heuristic to address this overhead by optimizing the maximum volume handled by a process. Experiments on synthetic communication graphs as well as real-world applications such as parallel Canonical Polyadic sparse tensor decomposition and parallel sparse matrix-dense matrix multiplication show that our approach is a powerful way of overcoming the bottlenecks posed by sparse and latency-bound irregular communication.

communication algorithm↗