X-ray studies of the mesogen 4- pentyl cyclohexyl -4- (4- propyl cyclohexyl) benzoate (HD35) has been conducted at various temperatures both in the aligned and non-aligned phases and molecular length/apparent layer thickness and average inter molecular distances determined. The order parameters in the SmecticB phase have been calculated as function of temperature. The molecular structure and charge density distribution in the minimum energy configuration has been obtained from molecular orbital calculations. This has been used to calculate intermolecular interaction energies using atom-atom potential function. Using a hexagonal type cell to simulate the SmB phase the lattice parameters have been calculated which are in good agreement with experimentally observed values. Using the energy values obtained from the DSC results in the McMillan potential, calculatons have been carried out and phase transition temperatures reproduced.