Mechanism and kinetics of sodium diffusion in Na-feldspar from neural network based atomistic simulations

IF 8.3 1区 材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY
Alexander Gorfer , Rainer Abart , Christoph Dellago
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Abstract

Alkali diffusion is a first-order control for microstructure and compositional evolution of feldspar during cooling from high temperatures of primary magmatic or metamorphic crystallization, and knowledge of the respective diffusion coefficients is crucial for reconstructing thermal histories. Our understanding of alkali diffusion in feldspar is, however, hindered by an insufficient grasp of the underlying diffusion mechanisms. We performed molecular dynamics simulations of sodium feldspar (Albite) containing different point defects using a recently developed neural network potential. A high degree of agreement between the sodium self-diffusion coefficients obtained from model simulations and those determined experimentally in earlier studies motivated a detailed investigation into the interstitial and vacancy mechanisms, corresponding jump rates, correlation factors and anisotropy. We identified a dumbbell shaped double occupancy of an alkali site as an important point defect and a correlation effect originating from the orientation of the dumbbell as a possible cause for the (001)>(010) diffusion anisotropy reported in numerous feldspar cation diffusion experiments.

Abstract Image

Abstract Image

基于神经网络原子模拟的钠长石中钠扩散机理和动力学
碱扩散是原生岩浆或变质结晶高温冷却过程中长石微观结构和成分演化的一级控制因素,了解各自的扩散系数对重建长石热历史至关重要。然而,我们对碱在长石中的扩散的理解受到对潜在扩散机制把握不足的阻碍。我们使用最近开发的神经网络电位对含有不同点缺陷的钠长石(钠长石)进行了分子动力学模拟。模型模拟得到的钠自扩散系数与早期实验确定的高度一致,促使我们对间隙和空位机制、相应的跳跃率、相关因素和各向异性进行了详细的研究。我们确定了一个哑铃形的碱基双占用是一个重要的点缺陷,并且由哑铃方向产生的相关效应是许多长石阳离子扩散实验中报道的⊥(001)>⊥(010)⊥(001)>⊥(010)扩散各向异性的可能原因。
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来源期刊
Acta Materialia
Acta Materialia 工程技术-材料科学:综合
CiteScore
16.10
自引率
8.50%
发文量
801
审稿时长
53 days
期刊介绍: Acta Materialia serves as a platform for publishing full-length, original papers and commissioned overviews that contribute to a profound understanding of the correlation between the processing, structure, and properties of inorganic materials. The journal seeks papers with high impact potential or those that significantly propel the field forward. The scope includes the atomic and molecular arrangements, chemical and electronic structures, and microstructure of materials, focusing on their mechanical or functional behavior across all length scales, including nanostructures.
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