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首页> 外文期刊>Physical review >Structural, vibrational, and thermodynamic properties of ordered and disordered Ni_(1-x)Pt_x alloys from first-principles calculations
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Structural, vibrational, and thermodynamic properties of ordered and disordered Ni_(1-x)Pt_x alloys from first-principles calculations

机译：根据第一性原理计算的有序和无序Ni_（1-x）Pt_x合金的结构，振动和热力学性质

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摘要

In terms of first-principles phonon calculations and the quasiharmonic approach, the structural, vibrational, and thermodynamic properties have been investigated for the ordered and disordered Ni_(1-x)Pt_x alloys, with the main focus being on disordered Ni_(0.5)5Pt_(0.5). To gain insight into the disordered alloys, we use special quasirandom structures (SQSs) and demonstrate their capabilities in predicting (i) the bond-length distributions, (ii) the phonon spectra, and (iii) the elastic stiffness constants of the disordered alloys. It is found that the Pt-Pt atomic pairs possess the longest bond lengths relative to the Ni-Pt and Ni-Ni ones in the disordered alloys, the predicted force constants indicate that the Pt-Pt bond is stiffer when compared to the Ni-Pt and the Ni-Ni ones for both the ordered and disordered alloys, and the phonon density of states of the disordered alloys are similar to the broadened versions of the ordered cases. Based on the results of the ordered and disordered alloys, a slightly positive deviation from Vegard's law is found for the volume variation of Ni_(1-x)Pt_x, and correspondingly, a negative deviation is predicted for the change of bulk modulus. With increasing Pt content, the bulk modulus derivative relative to pressure increases approximately linearly, whereas the magnetic moment decreases. In addition, the SQS-predicted relative energies (enthalpies of formation) for the disordered Ni_(1-x) Pt_x are also compared to cluster expansion predictions. As an application of the finite temperature thermodynamic properties, the phase transition between the ordered Llo and the disordered Ni_(0.5)Pt_(0.5) is predicted to be 755 ± 128 K, which agrees reasonably well with the measurement ~900 K, demonstrating that the driving force of the phase transition stems mainly from the configurational entropy rather than the vibrational entropy.
机译：在第一性原理声子计算和准谐波方法方面，研究了有序和无序Ni_（1-x）Pt_x合金的结构，振动和热力学性质，主要研究了无序Ni_（0.5）5Pt_。 （0.5）。为了深入了解无序合金，我们使用特殊的准随机结构（SQS）并展示了它们在预测（i）键长分布，（ii）声子谱和（iii）无序合金的弹性刚度常数方面的能力。 。发现无序合金中Pt-Pt原子对具有最长的键长，相对于Ni-Pt和Ni-Ni原子，预测的力常数表明与Ni-相比，Pt-Pt键更硬。有序合金和无序合金的Pt和Ni-Ni均无序，无序合金态的声子密度与有序情况的扩展形式相似。根据有序和无序合金的结果，发现Ni_（1-x）Pt_x的体积变化与Vegard定律略有正偏差，并相应地预测了体积模量变化的负偏差。随着Pt含量的增加，相对于压力的体积模量导数近似线性增加，而磁矩减小。此外，还将无序Ni_（1-x）Pt_x的SQS预测的相对能量（形成焓）与簇扩展预测进行了比较。作为有限温度热力学性质的一种应用，有序Llo和无序Ni_（0.5）Pt_（0.5）之间的相变预计为755±128 K，这与约900 K的测量值相当吻合，表明相变的驱动力主要来自构型熵，而不是振动熵。

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  • 来源
    《Physical review》 |2011年第14期|p.144204.1-144204.13|共13页
  • 作者

    S. L. Shang; Y. Wang; D. E. Kim; C. L. Zacherl; Y. Du; Z. K. Liu;

  • 作者单位

    Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;

    Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;

    Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;

    Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;

    State Key Laboratory of Powder Metallurgy, Central South University, Changshd, Hunan 410083, China;

    Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;

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  • 正文语种 eng
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  • 关键词

    transition metals and alloys;

    机译：过渡金属和合金;

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