| Title
A single sentence description.
|
Elastic constants for Si in AFLOW crystal prototype A_hR8_148_cf at zero temperature and pressure v000 |
|---|---|
| Description | Given the zero-pressure, zero-temperature structure of Si in AFLOW crystal prototype A_hR8_148_cf, this Test computes the corresponding elastic constants using numerical differentiation. By default, the Hessian of the energy w.r.t. strain is used, but depending on the computed uncertainty and material symmetry violation, the Jacobian of the stress w.r.t. strain may be used instead. |
| Species
The supported atomic species.
| Si |
| Disclaimer
A statement of applicability provided by the contributor, informing users of the intended use of this KIM Item.
|
Computer generated |
| Contributor |
I Nikiforov |
| Maintainer |
I Nikiforov |
| Published on KIM | 2024 |
| How to Cite | Click here to download this citation in BibTeX format. |
| Funding | Not available |
| Short KIM ID
The unique KIM identifier code.
| TE_520915061556_000 |
| Extended KIM ID
The long form of the KIM ID including a human readable prefix (100 characters max), two underscores, and the Short KIM ID. Extended KIM IDs can only contain alpha-numeric characters (letters and digits) and underscores and must begin with a letter.
| ElasticConstantsCrystal_A_hR8_148_cf_Si__TE_520915061556_000 |
| Citable Link | https://openkim.org/cite/TE_520915061556_000 |
| KIM Item Type | Test |
| Driver | ElasticConstantsCrystal__TD_034002468289_000 |
| Properties
Properties as defined in kimspec.edn.
These properties are inhereted from the Test Driver.
| |
| KIM API Version | 2.3 |
| Simulator Name
The name of the simulator as defined in kimspec.edn.
This Simulator Name is inhereted from the Test Driver.
| ase |
| Programming Language(s)
The programming languages used in the code and the percentage of the code written in each one.
| 100.00% Python |
| ElasticConstantsCrystal_A_hR8_148_cf_Si__TE_520915061556_000.txz | Tar+XZ | Linux and OS X archive |
| ElasticConstantsCrystal_A_hR8_148_cf_Si__TE_520915061556_000.zip | Zip | Windows archive |
This Test requires a Test Driver. Archives for the Test Driver ElasticConstantsCrystal__TD_034002468289_000 appear below.
| ElasticConstantsCrystal__TD_034002468289_000.txz | Tar+XZ | Linux and OS X archive |
| ElasticConstantsCrystal__TD_034002468289_000.zip | Zip | Windows archive |
In the original Stillinger-Weber paper (SW85: PRB 31:5262, 1985) it is stated that in order to obtain the correct “atomization energy” (cohesive energy) the following choice for epsilon must be made (see Eqn. (2.9) in [SW85]):
epsilon = 50 kcal/mol = 3.4723E-12 erg/atom
There are some unit conversion issues related to this data (see https://openkim.org/cite/MO_405512056662_003). However, a more fundamental problem is that in [SW85] the potential is fitted to an incorrect value for the cohesive energy of silicon. Using Eqn. (2.8) in [SW85], the cohesive energy corresponding to epsilon = 2.1682 eV (corresponding to 50 kcal/mol) is
E_coh = 2.168205112 eV x 1.999993 = 4.33639505 eV
However, the accepted experimental value for E_coh for silicon in the diamond structure is 4.63 eV. (See for example, B. Farid and R. W. Godby, “Cohesive energies of crystals”, Phys. Rev. B, vol 43, 14248-24250, 1991).
This discrepancy led Balamane, Halicioglu and Tiller in their review article of silicon potentials (H. Balamane, T. Halicioglu and W. A. Tiller, “Comparative study of silicon empirical interatomic potentials”, Phys. Rev. B, vol. 46, 2250-2279, 1992) to rescale the SW epsilon parameter to 2.315 eV which reproduces the experimental cohesive energy.
It is important to realize that the rescaled potential is completely different from the original SW potential. It will have different forces, different elastic constants, different activated processes, etc. Only equlibrium structures will be the same. Unfortunately, Balamane et al. did not state in their article that this rescaling was performed which has led to some confusion. (The fact that a rescaling was done was mentioned in an earlier article by the authors, Balamane et al., Phys. Rev. B, vol 40, 9999-10001. See last paragraph on p.9999.)
Balamane et al.’s rescaled SW potential may have merit, but it should not be confused with the original SW potential, which should use epsilon = 2.1682 eV (see https://openkim.org/cite/MO_405512056662_003)