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31 0 q EE^ll 6H =J +4Eg dz}T$(etectron ctoud)ole1 6}q, -d6I= "l-z gl= zlfdzl4 +d6I. E flzlE dzl*89 "J=q ^l-tr oJ4ol ++6Iq ++A.Jg 6].al €q. 4.92I<I9 oJqgE^l + q ++ rrlD,l4"J aEt*Bg qlgga(Van der Waals) E oJ4olell ++. He4 rJZ 9#zI: flzle+ TJol =l94ol azl9 dzlE +"Jq q 9lg el flz}9 d6IEs= t{t4oll flz|,l1-o]q1 oJqol 7)q $9q, *z'J + ?Bol "J"l4zl 9+=+. ole+ ,J+ ?C9zI9 flzlz}9 ^JE4L+e 0olr 9fzlr flzlE 44e=- tEzl 9*=tr1. lfl+ Ne, Ar9 flzlE {dJ{ol q+6}z'l"J FEaJ eA g "JE fzl 9l+. ol=E +C.J €zlol IrE vJfl- ^le4 oE E "ll flz}"_4ol zlz)? ed6lel +dr+ ++l= +F6Ia 9l= dzi9 +d6}el 6col r]=..Jzl6}f glq^l flzler] 4z)4 ++g zlzlT- llzl 9+= 4Z +d6}trl. dzlzl "19 +91. Et 9l = izJ faql. +g+ -9 d6lE +col qi+^] flzl9 4z)4 4ti(electrical dipoles) S+"I 9alr.l EC6I. d^Jg zVtl# flzlql f,t4"J 4^J+ Stg frtsrl4 J- e+E^l 27\E flzlzlqlE ql4ol Car+. ol4ol HI'JE^(van der waals)q-lq, gE zJ'J (London) oJ 4 ol a-lr ++. 5. 9ztE9 tslgg 4442|(crystal lattice) E. +rJ4z|(space lattice)4 6ll, 4 rE9l 'J t94z}(t9ls.: unit celI)-tr +^Jqq 9lq. 6. 44+ ol+= flz}9 *rJ4 HIgg 37IgE 4sal= C46Iq ,++E =lE+ql 4= {lgrJolg vJBolF9 ='Jgtr +Elg + gl4. azHg =Is+g x, y, ra9E a}_l r ^Iolzlol a, 9,74. ql +q ql+ tfl 7-14. a, b, celt 6|E ol=el tglrJ ole+ zJ rlololE taaale+ ol= aartle-l zlBol q= aAtgel +e€ oE E-+ Ul ola(Bravais)9 t4444zlB o-tr- +r}9 + g,ltrI. 7. (1) il c "J *4 zI: t94zI9 +rl= as ol rrE flzl?d&? 680/o0ll 4zI +ag 3z%oltr+. 4I"[3 T ot z ' Z )3 xZ F,-t VJ +0.6802