IONOV (a), V. S. LUBJMOV (a), L. A. MANAKOVA (a), V. S. ~N O V (b), and E. F. MAKAROV (b)The spectrum of collective excitations is investigated for the charge-ordered state of the first type, when the constants of the intra-and inter-site interactions correspond to electronic repulsion. Taking the interband exchange interaction into account the lower boundary of the spectrum is calculated and the conditions are determined when the collective mode is within the energy gap. It is shown that the considered excitations cause instability of the charge-ordered state with respect to the transition into the Mutt state, and the conditions of existence of such an instability are found. The collective spectrum of a one-dimensional crystal a t T = 0 is studied. B pa6oTe EiccnenyeTcn cIiercrp Icomemmximx ~0 3 6 y x~e m f i sap~~noao-ynop~~aoqemoro COCTOIIHUJI nepeoro pona, Korna KoHcTaaTbr BHYTPM-IZ MemuempoBoro BBPUMOs s a u~o~e f i c~s w~~ Bwmcaena nnmmFi rpamiua iionJrehimnoro cnempa w onpenenem YCJIOBHJI, npu IiOTOPbI?i KoaaemmHaII Moaa nemm BHYTPIZ 3~e p r e~~s e c~i o P uenri. no-& k T B M I I COOTBeTCTByIOT OTTaJIKUBaHIIIO 3JIeKTPOHOB. c Y W T O M MeH3OHHOrO 06MeHHOrO Ka3aH0, 9TO PaCCMOTpeHFiblt? BO36yHcZeHIIH 06YCX3BJlMBaIOT HeyCTOftWiBOCTb 3apHlJOBO-yllOpII~O~eI3HOrO COCTOHIIAII OTHOCUTeJIbHO IIepeXOna B YOTTOBCKOB COCTOHHMB II Onpene n e m ycnosm c y~~e c~~o s a r n s i TaIcoft H~C T~~U~L H O C T U . PaccMoTpea TaKme crremp KOJIZIt?HTUBHhlX B036YH(ZeHMfi IJIJI OaHOMepHOrO 1cpUCTanna IIpH T = 0 .vestigate the general problem of low-lying collective modes in COS I along the lines of papers [3,4].1) In Section 2 taking the interband exchange interaction into account l) I n [5] an attempt was made to determine the collective spectrum of electron pairs (the pair transfer) in Cs,SbCI, type compounds with SbCI; to SbC1:-concentration ratio of 1 :2. The spectrum ie in accordance with our work [6] in which the pair transfer in the Mossbauer effect was not observed. The pair transfer is found in C%SbCl, where t.he concentration ratio of SbC1; t o SbC1:ions i equal to 1 : 1 [4, ' 71. That is why the comparisons and conclusions made in [5] are meaningless.
The Thermodynamic Behaviour of Charge-Ordered Crystals BY V. S. LUBIMOV (a), L. A. MANAKOVA (a), E. F. MAKAROV (b), and S. P. IONOV (a) The influence is considered of the low lying collective excitations upon thermodynamic behaviour of charge-ordered states. The collective mode is found which provides the instability of this state relative to the Mott state when intra-(I) and intersite ( V ) interactions of electrons correspond to a repulsion. I f I < 0 and is stronger than the intersite repulsion, the collective excitations correspond to the motion of electron pairs. The energy and the specific heat are calculated and the phase diagram is qualihtively discussed as function of the I to V-ratio.
IONOV (a), V. S. LUBIMOV (a), L. A. MANAKOVA (a), and E. F. MAKAROV (b)The electronic excitation spectra for an isotropic charge-ordered crystal are analysed on the basis of a band model. It is found that the charge-ordered state is unstable relative to a transition into a state with pair correlation when the intra-band attraction among the electrons exceeds a certain critical value which is a function of the kinetic energy and interaction parameters. I n this situation a state is realized in which the charge order and the pair correlation are coexistent and which is possible a t a finite value of the band width. B p a 6 o~e a~an~3HpymTca Ha OCHOBe 30HHOg MOAeJIkl CIIeHTpbI 3JIeHTpOHHbIX B03-6ymaeHkla. YCTaHOBneHO, YTO 3apRHOBO-ynOpaAOseHHOe COCTORHHe HeCTa6ImbHO OTHOCHTeJIbHO IlepeXOAa B COCTORHkl e C IIapHO3 HOppeJIHqIIe3, HOrAa BHYTPH30HHOe IIpklTHHEeHHe 3JIeKTpOHOB IIpeBbIIXaeT OIIpeneJIeHHyIO HpMTIIYeCKYH) BeJIII9klHY, HOTOpaR eCTb $lYHHUIIR ECMHeTkl W!Cl EOj i 3Heprllkl kl IIapaMeTpOB B3aIIMORekTBIIR. B 3 T 0 3 CIITYaqklH BYIoT OnHOBpeMeHHO II HOTOpOe B03MOHEHO JIIIUb IIpH HOHeYHOl% IXklpIIHe 3OHM.p e a m m y e~c~ cocTomne, B HOTOPOM 3ap~ao~b1fi n o p~~o~ II napHaH Hoppenasm cyuecT-
Mössbauer spectra and lifetime positron distributions are studied for BaPb0.99−xSn0.01BixO3 samples with 0 ≦ x ≦ 0.4 containing Sn119 as Mössbauer label. A correlation is observed between the dependence of room temperature parameters of Mössbauer and positron spectra on x and transition temperatures to superconducting state Tc(x). The data obtained are interpreted in terms of bielectron transfer over bismuth centers.
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