The macro in this page returns Atomic Weight based on Atomic Symbol.

Below atomic weight data were copied from the “Standard Atomic Weight” column in the “isotopes.txt” file in the TOPAS installation folder.

The atomic weight of some heavy atoms after No.109 are from www.periodictable.one

This macro has been tested working in v6 and v7.

macro AW {Atomic_Weight}
macro Atomic_Weight(Atom) {					
#if 
 (Atom == "H")	1.00794   	#elseif
 (Atom == "He")	4.002602  	#elseif
 (Atom == "Li")	6.941     	#elseif
 (Atom == "Be")	9.012182  	#elseif
 (Atom == "B")	10.811    	#elseif
 (Atom == "C")	12.0107   	#elseif
 (Atom == "N")	14.0067   	#elseif
 (Atom == "O")	15.9994   	#elseif
 (Atom == "F")	18.9984032	#elseif
 (Atom == "Ne")	20.1797   	#elseif
 (Atom == "Na")	22.989770 	#elseif
 (Atom == "Mg")	24.3050   	#elseif
 (Atom == "Al")	26.981538 	#elseif
 (Atom == "Si")	28.0855   	#elseif
 (Atom == "P")	30.973761 	#elseif
 (Atom == "S")	32.065    	#elseif
 (Atom == "Cl")	35.453    	#elseif
 (Atom == "Ar")	39.948    	#elseif
 (Atom == "K")	39.0983   	#elseif
 (Atom == "Ca")	40.078    	#elseif
 (Atom == "Sc")	44.955910 	#elseif
 (Atom == "Ti")	47.867    	#elseif
 (Atom == "V")	50.9415   	#elseif
 (Atom == "Cr")	51.9961   	#elseif
 (Atom == "Mn")	54.938049 	#elseif
 (Atom == "Fe")	55.845    	#elseif
 (Atom == "Co")	58.933200 	#elseif
 (Atom == "Ni")	58.6934   	#elseif
 (Atom == "Cu")	63.546    	#elseif
 (Atom == "Zn")	65.409    	#elseif
 (Atom == "Ga")	69.723    	#elseif
 (Atom == "Ge")	72.64     	#elseif
 (Atom == "As")	74.92160  	#elseif
 (Atom == "Se")	78.96     	#elseif
 (Atom == "Br")	79.904    	#elseif
 (Atom == "Kr")	83.798    	#elseif
 (Atom == "Rb")	85.4678   	#elseif
 (Atom == "Sr")	87.62     	#elseif
 (Atom == "Y")	88.90585  	#elseif
 (Atom == "Zr")	91.224    	#elseif
 (Atom == "Nb")	92.90638  	#elseif
 (Atom == "Mo")	95.94     	#elseif
 (Atom == "Tc")	98    		#elseif
 (Atom == "Ru")	101.07    	#elseif
 (Atom == "Rh")	102.90550 	#elseif
 (Atom == "Pd")	106.42    	#elseif
 (Atom == "Ag")	107.8682  	#elseif
 (Atom == "Cd")	112.411   	#elseif
 (Atom == "In")	114.818   	#elseif
 (Atom == "Sn")	118.710   	#elseif
 (Atom == "Sb")	121.760   	#elseif
 (Atom == "Te")	127.60    	#elseif
 (Atom == "I")	126.90447 	#elseif
 (Atom == "Xe")	131.293   	#elseif
 (Atom == "Cs")	132.90545 	#elseif
 (Atom == "Ba")	137.327   	#elseif
 (Atom == "La")	138.9055  	#elseif
 (Atom == "Ce")	140.116   	#elseif
 (Atom == "Pr")	140.90765 	#elseif
 (Atom == "Nd")	144.24    	#elseif
 (Atom == "Pm")	145    		#elseif
 (Atom == "Sm")	150.36    	#elseif
 (Atom == "Eu")	151.964   	#elseif
 (Atom == "Gd")	157.25    	#elseif
 (Atom == "Tb")	158.92534 	#elseif
 (Atom == "Dy")	162.500   	#elseif
 (Atom == "Ho")	164.93032 	#elseif
 (Atom == "Er")	167.259   	#elseif
 (Atom == "Tm")	168.93421 	#elseif
 (Atom == "Yb")	173.04    	#elseif
 (Atom == "Lu")	174.967   	#elseif
 (Atom == "Hf")	178.49    	#elseif
 (Atom == "Ta")	180.9479  	#elseif
 (Atom == "W")	183.84    	#elseif
 (Atom == "Re")	186.207    	#elseif
 (Atom == "Os")	190.23     	#elseif
 (Atom == "Ir")	192.217     	#elseif
 (Atom == "Pt")	195.078     	#elseif
 (Atom == "Au")	196.96655   	#elseif
 (Atom == "Hg")	200.59    	#elseif
 (Atom == "Tl")	204.3833    	#elseif
 (Atom == "Pb")	207.2    	#elseif
 (Atom == "Bi")	208.98038   	#elseif
 (Atom == "Po")	209   		#elseif
 (Atom == "At")	210   		#elseif
 (Atom == "Rn")	222   		#elseif
 (Atom == "Fr")	223   		#elseif
 (Atom == "Ra")	226   		#elseif
 (Atom == "Ac")	227   		#elseif
 (Atom == "Th")	232.0381    	#elseif
 (Atom == "Pa")	231.03588   	#elseif
 (Atom == "U")	238.02891   	#elseif
 (Atom == "Np")	237   		#elseif
 (Atom == "Pu")	244   		#elseif
 (Atom == "Am")	243   		#elseif
 (Atom == "Cm")	247   		#elseif
 (Atom == "Bk")	247   		#elseif
 (Atom == "Cf")	251   		#elseif
 (Atom == "Es")	252   		#elseif
 (Atom == "Fm")	257   		#elseif
 (Atom == "Md")	258   		#elseif
 (Atom == "No")	259   		#elseif
 (Atom == "Lr")	262   		#elseif
 (Atom == "Rf")	261   		#elseif
 (Atom == "Db")	262   		#elseif
 (Atom == "Sg")	266   		#elseif
 (Atom == "Bh")	264   		#elseif
 (Atom == "Hs")	277   		#elseif
 (Atom == "Mt")	268   		#elseif
 (Atom == "Ds")	281   		#elseif
 (Atom == "Rg")	272   		#elseif
 (Atom == "Cn")	285   		#elseif
 (Atom == "Nh")	286   		#elseif
 (Atom == "Fl")	289   		#elseif
 (Atom == "Mc")	289   		#elseif
 (Atom == "Lv")	293   		#elseif
 (Atom == "Ts")	294   		#elseif
 (Atom == "Og")	294   		#endif					
}				

RAW(corundum) 
 
   CuKa5(0.001)      
   Radius(173)
   LP_Factor(26.6)
   Full_Axial_Model(12, 15, 12, 4.6, 4.6)
   Slit_Width(0.3)
   Divergence(1)           
 
   Absorption(@, 26)
 
   ZE(@, 0.0)
 
   One_on_X(@, 0)
   bkg  @ 0 0 0 0 0 0
 
   STR(R_-3_C)
      phase_name "Corundum"
      Trigonal(@ 4.7592, @ 12.992)
      site Al    x   0        y 0       z @ 0.35228  occ Al   1   beq @ 0.32 
      site O     x @ 0.3064   y 0       z   0.25     occ O    1   beq @ 0.33  
      scale @  0.0001
      CS_L(@, 100)
      Strain_L(@, 0.0100)
      view_structure
      r_bragg 0
      local mol_wgt = 2 * AW("Al") + 3 * AW("O");: 101.961276 'User type in this equation from known molecular formule
      local cell_Z = Round(Get(cell_mass)/mol_wgt);:6 ' Molecule number in cell is automatically updated after refinement.

If any user in our open TOPAS community has suggestion or idea, or bug report on these macros, please kindly let me know and I am happy to learn from you: tony.wang@qut.edu.au