I have been using the code below in TOPAS7 for PONKCS, however after we upgraded to TOPAS8, after running the same code, I get this error. Also after removing the xo_Is section from the end the code works fine. This is the error I get:

(*** Error loading sstring_in
at LINE 221
See log file C:\Users\User\Desktop\TOPAS-8\topas.log
Cannot locate cell_volume from xi in data structures
)

I have attached my entire code here

'-------------------------------------------------------------- 
'Input File for simple Rietveld Refinement 
'Replace any $, # or text after ---> as needed 
'Use Ta-> button to save/send to topas; Ta button to launch topas; run in topas with red arrow 
'-------------------------------------------------------------- 
r_wp  4.68113812 r_exp  1.86894489 r_p  3.37185696 r_wp_dash  12.6982291 r_p_dash  11.7108446 r_exp_dash  5.06976933 weighted_Durbin_Watson  0.141129327 gof  2.50469564
 
'-------------------------------------------------------------- 
'General information about refinement here 
'Remove commented lines as required 
'-------------------------------------------------------------- 
iters 100000 
chi2_convergence_criteria 0.001 
'do_errors 
 
'-------------------------------------------------------------- 
'Information on datafile etc here 
'Check that default weighting is appropriate for your data 
'-------------------------------------------------------------- 
xdd Original-made(5-30-2025)CT(6-9-25)(5)_Theta_2-Theta.xy 
	x_calculation_step = Yobs_dx_at(Xo); convolution_step 4 
 
			bkg @  2219.67329` -1825.83258`  682.255263` -219.615877`  108.645706` -81.1303503` -15.093359` -6.33007113`  32.1710267`  31.2794335`
	'd5000 Bragg Brentano Sol-X Cu Ka1/a2 2 line emission 	
			Radius(150)
		Divergence( 1.24550168)
	  	axial_conv                    
		filament_length			  10
		sample_length				  24.00000
		receiving_slit_length     13
		primary_soller_angle	     5
		secondary_soller_angle    5

	Tube_Tails(, 0.00392148868_LIMIT_MIN_1e-05, , -5_LIMIT_MIN_-5,, 3.72538992, , 1.00014257e-05_LIMIT_MIN_1e-05)

		lam
		ymin_on_ymax  0.0001
		la   0.01346 lo   1.5348157 lh   3.85592_LIMIT_MAX_5
		la   0.25303 lo   1.5410084 lh   0.00000_LIMIT_MIN_1e-06
		la   0.00085_LIMIT_MIN_1e-05 lo   1.5464449_LIMIT_MAX_1.55644488 lh   0.02459_LIMIT_MIN_1e-06
		la   0.13343 lo   1.5448221 lh   0.00000_LIMIT_MIN_1e-06
		la   0.00366 lo   1.5470017 lh   0.00019_LIMIT_MIN_1e-06
		
	LP_Factor(!th2_monochromator, 0)

	Zero_Error(zero, 0.28054603`)

	Absorption(@, 61.7552124`)


	str  
		phase_name "Brucite"  
		space_group "P-3m1"  
		al 90       
		be 90       
		ga 120 
		a a_brucite  3.149924`
		b @ = a_brucite ;:  3.149924`
		c @  4.798774`   
		volume 40.7       
		site Mg1    x 0.            y 0.            z 0.            occ Mg+2 1.        							  beq 0.2
		site O1     x =1/3;        y =2/3;        z @  0.22216`     occ O-2  1.        							  beq 0.2   
		site H1     x =1/3;        y =2/3;        z @  0.37981` occ H  1.              beq 0.2
                                                                                     
		scale @  0.381781287`
		r_bragg  2.03464625
		Phase_Density_g_on_cm3( 2.34856953`)  
		
		MVW( 58.320, 41.235`, 16.374`)  
		LVol_FWHM_CS_G_L(1, 7.94881314`, 0.89, 11.1051089`, @, 3286.36212`_LIMIT_MIN_0.3,@, 12.4712579`)  
		e0_from_Strain( 7.43507349e-07`, @, 0.000252584839`_LIMIT_MIN_0.0001, @, 0.000146558442`_LIMIT_MIN_0.0001) 
  
  
	str  
		phase_name "Periclase"  
		space_group "Fm-3m"  
		al 90       
		be 90       
		ga 90 
		a lpa5  3.676675`
		b lpa5  3.676675`
		c lpa5  3.676675`
		volume  49.701`   
		site Mg1    x 0.            y 0.            z 0.            occ Mg+2 1.      beq 2.43187052 			min 0    
		site O1     x 0.5           y 0.5           z 0.5           occ O-2  1.      beq 1.65019786        min 0    
		scale @ 0.0001                                                            
		r_bragg 0                                                                 
		Phase_Density_g_on_cm3( 5.38637064`)  
		scale @  0.0117314645`
		r_bragg  0.265380645
      
		LVol_FWHM_CS_G_L(1, 9.39019672`, 0.89, 8.89995401`, @, 10.0058398`,@, 9995.11733`_LIMIT_MIN_0.3)  
		e0_from_Strain( 0.000941806498`, @, 0.431634273`_LIMIT_MIN_0.0001, @, 0.0001`_LIMIT_MIN_0.0001) 
		
  
	str  
		phase_name "5Phase"
		space_group "P12/m1"  
		al 90       
		be 113.986  
		ga 90  
		a @  9.661104` 
		b @  3.158245` 
		c @  8.329149` 
		volume  232.194`  
		site Mg1    x @  0.80109`     y 0             z @  0.69145`     occ Mg   1          beq 4.91901083    		 min 0 
		site Mg2    x   0.5           y 0.5           z   0.5           occ Mg   1          beq 4.91901083           min 0 
		site Cl1    x cl1_x   0.69057`     y 0.5           z cl1_z   0.10759`     occ Cl cl1  0.66421` min 0 max 1       beq   10.86072          min 0 
		site O1     x @  0.73355`     y 0.5           z @  0.50755`     occ O    1          beq 4.91901083           min 0 
		site O2     x @  0.57753`     y 0             z @  0.70094`     occ O    1          beq 4.91901083           min 0 
		site O3     x @  1.03677`     y 0             z @  0.67583`     occ O    1          beq 4.91901083           min 0 
		site O4     x @  0.86695`     y 0.5           z @  0.90041`     occ O    1          beq 4.91901083           min 0 
		site O5     x = cl1_x ;      y 0.5           z = cl1_z ;     occ O  o5 = 1 - cl1;        beq  19.98302
		site H1     x @  0.91737`     y 0.5           z @  0.50581`     occ H    1          beq 4.91901083           min 0 
		site H2     x @  0.41063`     y 0             z @  0.68927`     occ H    1          beq 4.91901083           min 0 
		site H3     x @  1.37878`     y  -0.1875       z @  0.76409` occ H    0.5        beq 4.91901083           min 0 
		site H4     x @  1.07063`     y  0.1875        z @  0.64673`   occ H    0.5        beq 4.91901083           min 0 
		site H5     x @  0.50082`_LIMIT_MAX_0.604285487 y 0.5           z @  1.08670`     occ H    0.75       beq @  0.08621`_LIMIT_MIN_0 min 0 
		site H6     x @  0.92158` y 0.5           z @  1.29456`     occ H    0.75       beq @  0.01407`_LIMIT_MIN_0 min 0 
		site H7     x @  0.88028`_LIMIT_MAX_0.983742649 y 0.5           z @  0.13108`_LIMIT_MAX_0.251276436 occ H    0.5        beq @  0.00183`_LIMIT_MIN_0 min 0 
		site H8     x @  0.36326`_LIMIT_MAX_0.466724813 y 0.5           z @ -0.23713` occ H    0.5        beq @  0.00732`_LIMIT_MIN_0 min 0 
  
		scale @  0.0615506937`
		r_bragg  1.6213019
		'TCHZ_Peak_Type(pku, 0.064487057_LIMIT_MAX_0.164487057,pkv, -0.115885093,pkw,  0.0329015342,!pkz, 0.0000,pkx, 0.000100000222_LIMIT_MIN_0.0001, pky, 0.282294863)  
		Phase_Density_g_on_cm3( 1.94417666`)   
		LVol_FWHM_CS_G_L(1, 15.7966042`, 0.89, 22.0281599`, @, 931.401974`_LIMIT_MIN_0.3,@, 24.7167576`)  
		e0_from_Strain( 0.000489019981`, @, 0.224060409`_LIMIT_MIN_0.0001, @, 0.000153643738`_LIMIT_MIN_0.0001) 
  prm = cl1 + o5 ; :  1`
		

'--------------------------------------------------------------
'Information on structure
'Change recurring numbers in coordinates as required e.g. 0.3333 to =1/3;
'--------------------------------------------------------------
	str
		phase_name "Korshunovskite"
		space_group "P-1"
		al 101.97   
		be 104.0    
		ga 73.18    
		a @  8.442657`_LIMIT_MIN_8.2586916
		b @  6.223246`_LIMIT_MIN_6.06141961
		c @  7.311298`_LIMIT_MIN_7.13861794
		volume 370.154  
		site Mg1    x 0.05500       y 0.40000       z 0.18800       occ Mg   1
		site Mg2    x 0.05500       y 0.90000       z 0.18800       occ Mg   1
		site O-HII1 x 0.14400       y 0.10000       z 0.03900       occ O    1
		site O-HII2 x 0.14400       y 0.60000       z 0.03900       occ O    1
		site O-HI   x -0.04200      y 0.22000       z 0.31600       occ O    1
		site Cl     x -0.43800      y 0.81200       z 0.18800       occ Cl   1
		site WatI   x -0.04200      y 0.72000       z 0.31600       occ O    1
		site WatII  x 0.27800       y 0.86100       z 0.39400       occ O    1
		site WatIII x 0.27800       y 0.36100       z 0.39400       occ O    1
		site WatIV  x -0.41600      y 0.31900       z 0.25000       occ O    1

		scale @  0.000117865689`_LIMIT_MIN_1e-15
		r_bragg  2.94522305
		'TCHZ_Peak_Type(pku, 0.00039,pkv, -0.00221,pkw, -0.00146,!pkz, 0.0000,pkx, 0.00957, pky, 0.0001)
		Phase_Density_g_on_cm3( 1.84528964`)  
 
		 MVW( 392.118, 352.859`, 0.291`)  
		LVol_FWHM_CS_G_L(1, 34.0957464`, 0.89, 32.351338`, @, 36.428093`_LIMIT_MIN_0.3,@, 9976.86601`_LIMIT_MIN_0.3)  
		e0_from_Strain( 5.10231444e-07`, @, 0.000131572056`_LIMIT_MIN_0.0001, @, 0.000156002908`_LIMIT_MIN_0.0001) 
		  

'--------------------------------------------------------------
'Information on structure
'Change recurring numbers in coordinates as required e.g. 0.3333 to =1/3;
'--------------------------------------------------------------
	str
		phase_name "Chloroartinite"
		space_group "R3c:H"
		al 90.0     
		be 90.0     
		ga 120.0    
		a lpa1  23.445497`_LIMIT_MIN_23.1118778
		b lpa1  23.445497`
		c @  7.004734`_LIMIT_MIN_6.83511227
		volume 3350.84  
		site Cl1    x 0.15058       y 0.19895       z -0.1824       occ Cl-1 1.0        beq 2.43187052   
		site Mg1    x 0.2847        y 0.1193        z -0.0737       occ Mg+2 1.00       beq 1.65019786   
		site Mg2    x 0.2800        y 0.3149        z 0.3367        occ Mg+2 1.00       beq 1.45280577   
		site O1     x 0.1859        y 0.0937        z -0.0918       occ O-2  1.00       beq 5.84280581   
		site O2     x 0.2959        y 0.1845        z 0.1532        occ O-2  1.00       beq 1.07381296   
		site O3     x 0.3207        y 0.2257        z -0.1268       occ O-2  1.00       beq 1.07381296   
		site O4     x 0.3189        y 0.2873        z 0.1151        occ O-2  1.0        beq 1.07381296   
		site O5     x 0.2660        y 0.2374        z 0.5035        occ O-2  1.0        beq 0.236870506  
		site O6     x 0.1885        y 0.2766        z 0.1732        occ O-2  1.0        beq 2.28974822   
		site O7     x 0.0113        y 0.0704        z -0.035        occ O-2  0.4        beq 11.3697843   
		site O8     x 0.0078        y 0.0846        z -0.246        occ O-2  0.6        beq 11.1329138   
		site C1     x 0.3046        y 0.2308        z 0.0423        occ C  1.00       beq 1.07381296   

		scale @  2.23810486e-06`_LIMIT_MIN_1e-15
		r_bragg  0.80786978
		'TCHZ_Peak_Type(pku, 0.00039,pkv, -0.00221,pkw, -0.00146,!pkz, 0.0000,pkx, 0.00957, pky, 0.0001)
		Phase_Density_g_on_cm3( 1.86504425`)
		 MVW( 3745.251, 3334.580`, 0.498`)  
		LVol_FWHM_CS_G_L(1, 26.9222298`, 0.89, 36.8729095`, @, 179.90501`_LIMIT_MIN_0.3,@, 43.8638306`_LIMIT_MIN_0.3)  
		e0_from_Strain( 0.0109690562`, @, 4.99993041`_LIMIT_MIN_0.0001, @, 0.0481233034`_LIMIT_MIN_0.0001) 

		 
xo_Is
phase_name Brucite_pks
MVW( 58.320, 41.037, 6.402`)
CS_L(!cs2, 45)
peak_type fp
scale    0.15

    xo   !pos3    58.5244
    I    !int3    2500
    
    xo_Is
phase_name 5Phase_pks
MVW( 265.466, 230.973, 5.468`)
CS_L(!cs1, 50)
peak_type fp
scale    0.005

    xo   !pos1    11.80287
    I    !int1    4500
    xo   !pos5    21.38204
    I    !int5    4000
    xo   !pos6    33.90238
    I    !int6    4000