{
    "property-id" "tag:tadmor@noreply.openkim.org,2017-02-01:property/verification-check" 
    "instance-id" 1 
    "vc-name" {
        "source-value" "vc-inversion-symmetry"
    } 
    "vc-description" {
        "source-value" "Check whether a model is invariant with respect to the inversion operation where each atom is moved along a straight line through the inversion center to a point of equal distance on the other side. This is satisfied for all inversion centers if the model is invariant to rigid-body translation, and has inversion symmetry about the origin. Invariance symmetry is expected from the properties of the quantum mechanics Hamiltonian operator. It should be true for any model that does not depend on an external field. The check is performed for a randomly distorted non-periodic body-centered cubic (BCC) cube base structure. Separate configurations are tested for each species supported by the model, as well as one containing a random distribution of all species.  The energy and forces of each configuration are compared with those of the same configuration translated in a random direction by an irrational distance and then inverted through the origin. The energies must be the same and the forces must change sign.  The verification check will pass if the energy of all configurations that the model is able to compute pass both tests. Configurations used for testing are provided as auxiliary files."
    } 
    "vc-category" {
        "source-value" "informational"
    } 
    "vc-grade-basis" {
        "source-value" "passfail"
    } 
    "vc-grade" {
        "source-value" "F"
    } 
    "vc-comment" {
        "source-value" "Model energy does NOT have inversion symmetry for at least one configuration that the model was able to compute. This could be valid if the model includes an external field or represents a material with unusual quantum properties. Otherwise this is an error in the model implementation."
    } 
    "vc-files" {
        "source-value" [
            "config-Al.xyz" 
            "config-Li.xyz" 
            "config-AlLi.xyz"
        ]
    }
}