1. Institute of Inorganic Chemistry, Slovak Academy of Sciences, 845 36 Bratislava, Slovakia
2. Conditions Extrêmes ét Matériaux: Haute Température et Irradiation, CEMHTI, UPR 3079-CNRS Univ. Orléans, 450 71, Orléans, France
3. Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice, Slovakia