Structural stability of higher-energy phases and its relation to the atomic configurations of extended defects: The example of Cu

Structure, energetics, and mechanical stability of Fe-Cu bcc alloys from first-principles calculations

“…Note in particular that the current GGA result of CЈ = −14.5 GPa for bcc Cu is considerably more negative ͑by 8.5 GPa͒ than the value calculated by LDA in the work of Wang et al. 36,37 Table III presents a comparison between our results for atomic volume, bulk modulus, and formation energy ͑⌬E form ͒, and previously published GGA calculations for ordered bcc-based Fe-Cu compounds. Very good overall agreement is found between the current and previous calculations.…”

A molecular dynamics study of the role of grain size and orientation on compression of nanocrystalline Cu during shock

“…For both transformation paths, the FCC to BCC phase transformation occurs by compression. Additional details on the tetragonal and trigonal phase transformation paths in copper can be obtained in [45]. Fig.…”

“…Although some authors have reported that the BCC phase of Cu is unstable energetically [41,42] and mechanically [41,43], other authors have argued that under certain mechanical constraints, the BCC phase of Cu can be lower in energy than the FCC phase [44,45] and mechanically stable [46]. For example, Wang and Sob [45] showed that BCC Cu can be energetically stable if the lattice is restricted to deform along a trigonal deformation path. Also, recent ab initio calculations by Mei et al [46] showed that BCC Cu under hydrostatic pressure becomes mechanically stable at 7.5 GPa compression, as shown by a change in the sign of the tetragonal shear modulus from negative to positive, and stability continues to increase with increasing hydrostatic compression.…”

Higher-energy Structures and Stability of Cu and Al Crystals Along Displacive Transformation Paths

“…When we ascribe p = 1 for the bcc structure, the fcc structure is obtained for p = √ 2. The trigonal path [10,13] is shown in Figure 2. Starting again from bcc lattice, the deformation can be described by the same Lagrangian deformation tensor (1) as in case of the tetragonal path with the coordinate system with x, y and z axes parallel to [110], [112] and [111], respectively.…”

“…The distorted structures studied correspond to configurations obtained along three types of transformation paths that connect body-centred cubic (bcc), face-centred cubic (fcc), simple cubic (sc) and hexagonal close-packed (hcp) lattices. Let us note here that the stability of higher-energy phases along such transformation paths has been previously studied extensively using ab initio calculations [8][9][10][11][12][13][14], but only a few studies have been concerned with testing semi-empirical potentials by analyzing the behavior of total energy along the displacive transformation paths [3,[15][16][17]. In each case, systematic comparison of the total energies of highly distorted configurations obtained from ab initio and semi-empirical calculations reveals the limitations of the semi-empirical approaches.…”